PYSEC-2026-177

Vulnerability from pysec - Published: 2026-05-28 16:16 - Updated: 2026-06-02 10:34
VLAI
Details

PyJWT is a JSON Web Token implementation in Python. Prior to 2.13.0, PyJWKClient.get_signing_key() forces a fresh HTTP request to the JWKS endpoint for every JWT with an unknown kid value, with no rate limiting. Since kid comes from the unverified token header, an attacker can trigger unlimited outbound requests. The vulnerability surfaces only when a JWKS fetch fails; an attacker can attempt to provoke that with sustained unknown-kid traffic, but the outcome depends on upstream JWKS-endpoint behavior (rate limiting, transient errors) which is beyond the attacker's control. This vulnerability is fixed in 2.13.0.

Severity
3.7 (Low)
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
Impacted products
Name purl
pyjwt pkg:pypi/pyjwt
Aliases
To clipboard 

{
  "affected": [
    {
      "ecosystem_specific": {},
      "package": {
        "ecosystem": "PyPI",
        "name": "pyjwt",
        "purl": "pkg:pypi/pyjwt"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "2.13.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "0.1.1",
        "0.1.2",
        "0.1.3",
        "0.1.4",
        "0.1.5",
        "0.1.6",
        "0.1.7",
        "0.1.8",
        "0.1.9",
        "0.2.0",
        "0.2.1",
        "0.2.3",
        "0.3.0",
        "0.3.1",
        "0.3.2",
        "0.4.0",
        "0.4.1",
        "0.4.2",
        "0.4.3",
        "1.0.0",
        "1.0.1",
        "1.1.0",
        "1.3.0",
        "1.4.0",
        "1.4.1",
        "1.4.2",
        "1.5.0",
        "1.5.1",
        "1.5.2",
        "1.5.3",
        "1.6.0",
        "1.6.1",
        "1.6.3",
        "1.6.4",
        "1.7.0",
        "1.7.1",
        "2.0.0",
        "2.0.0a1",
        "2.0.0a2",
        "2.0.1",
        "2.1.0",
        "2.10.0",
        "2.10.1",
        "2.11.0",
        "2.12.0",
        "2.12.1",
        "2.2.0",
        "2.3.0",
        "2.4.0",
        "2.5.0",
        "2.6.0",
        "2.7.0",
        "2.8.0",
        "2.9.0"
      ]
    }
  ],
  "aliases": [
    "CVE-2026-48524",
    "GHSA-fhv5-28vv-h8m8"
  ],
  "details": "PyJWT is a JSON Web Token implementation in Python. Prior to 2.13.0, PyJWKClient.get_signing_key() forces a fresh HTTP request to the JWKS endpoint for every JWT with an unknown kid value, with no rate limiting. Since kid comes from the unverified token header, an attacker can trigger unlimited outbound requests. The vulnerability surfaces only when a JWKS fetch fails; an attacker can attempt to provoke that with sustained unknown-kid traffic, but the outcome depends on upstream JWKS-endpoint behavior (rate limiting, transient errors) which is beyond the attacker\u0027s control. This vulnerability is fixed in 2.13.0.",
  "id": "PYSEC-2026-177",
  "modified": "2026-06-02T10:34:21.056558Z",
  "published": "2026-05-28T16:16:29.403Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://github.com/jpadilla/pyjwt/security/advisories/GHSA-fhv5-28vv-h8m8"
    }
  ],
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L",
      "type": "CVSS_V3"
    }
  ]
}


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