CVE-2026-102273: PyJWT PyJWT Accepts Public JWK Containers Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-w2cx-738m-mc7w",
  "modified" : "2026-09-29T23:16:55Z",
  "published" : "2026-09-29T23:16:55Z",
  "aliases" : [ "CVE-2026-102273" ],
  "summary" : "PyJWT accepts public JWK containers as HMAC secrets",
  "details" : "### Summary\n\nPyJWT 2.13.0 contains an incomplete defense against algorithm confusion when\nan application mixes symmetric and asymmetric algorithms in one verification\npath. A public RSA, EC, or OKP JWK can be accepted as an HMAC secret when it\nis wrapped in a JWKS object, nested in an array, or represented in another\ncontainer form that does not expose a top-level `kty` member.\n\n### Impact\n\nAn attacker who knows the public key material can forge HS256/HS384/HS512\ntokens if the application simultaneously:\n\n* allows both HS* and asymmetric algorithms;\n* passes raw public JWK/JWKS JSON as `key=`; and\n* uses that same value as the HMAC secret.\n\nThis can allow forged JWT claims in affected application configurations. The\nissue does not affect applications that keep symmetric and asymmetric\nverification paths separate and follow PyJWT's algorithm-selection guidance.\n\n### Fix status\n\nThe fix is on `master` in commit `801cd12` (`fix: reject public JWK container\nHMAC keys`). `HMACAlgorithm.prepare_key` now rejects public JWK members found in\nobjects, arrays, nested containers, BOM/UTF variants, and recursion-limit\ninputs. It also recognizes escaped JSON member names without treating ordinary\nstring values as JWKs. Ordinary JSON secrets remain accepted byte-for-byte.\n\nThe change was tested with focused regression tests and the full local tox\nmatrix. Available Python 3.9, 3.12, and 3.13 crypto/no-crypto suites, mypy,\npackage metadata, and coverage passed; unavailable interpreters were skipped\nby the project configuration. A fresh independent Astra/max security review\naccepted the final diff with no blocking findings.\n\nThe affected range is `= 2.13.0`. The fix is on the unreleased development\nbranch; the patched version will be recorded when a released 2.x version\ncontaining the fix is available. This advisory is being moved to draft pending\nthat release.\n\n### Reporter credit\n\nCredit: Charles Vosburgh / Trilobyte.\n\n### Original report\n\nThe original report and reproduction package are retained in the private\nadvisory record.\n\n## Maintainer update — 2026-09-11\n\nThe verified fix for this advisory is included in PyJWT 2.14.0, released on 2026-09-11 and available on PyPI. PyJWT 2.14.0 is the first release containing the fix. This advisory is now published with 2.14.0 recorded as the patched version.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "PyJWT"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "2.13.0"
      }, {
        "fixed" : "2.14.0"
      } ]
    } ],
    "versions" : [ "2.13.0" ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/jpadilla/pyjwt/security/advisories/GHSA-w2cx-738m-mc7w"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-102273"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/jpadilla/pyjwt/commit/801cd128528c62d9b23fcd161d1a2e1c17982f95"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/jpadilla/pyjwt"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/jpadilla/pyjwt/releases/tag/2.14.0"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-347" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-09-29T23:16:55Z",
    "nvd_published_at" : "2026-09-28T21:17:15Z"
  }
}