NIXPKGS-2026-1789

GitHub issue published on

Permalink CVE-2026-48523

5.4 MEDIUM

CVSS version (CVSS): 3.1
Attack Vector (AV): Network (N)
Attack Complexity (AC): Low (L)
Privileges Required (PR): Low (L)
User Interaction (UI): None (N)
Scope (S): Unchanged (U)
Confidentiality (C): Low (L)
Integrity (I): Low (L)
Availability (A): None (N)
Modified Attack Vector (MAV): Network (N)
Modified Attack Complexity (MAC): Low (L)
Modified Privileges Required (MPR): Low (L)
Modified User Interaction (MUI): None (N)
Modified Confidentiality (MC): Low (L)
Modified Scope (MS): Unchanged (U)
Modified Integrity (MI): Low (L)
Modified Availability (MA): None (N)

updated 13 hours ago by @LeSuisse Activity log

Created suggestion 2 days, 23 hours ago
@LeSuisse accepted 2 days, 16 hours ago
@LeSuisse published on GitHub 13 hours ago

PyJWT: Algorithm allow-list bypass when decoding with `PyJWK` / `PyJWKClient` keys

PyJWT is a JSON Web Token implementation in Python. From 2.9.0 to 2.12.1, there is a verifier-side algorithm allow-list bypass when jwt.decode() or jwt.decode_complete() are called with a PyJWK key. The token header alg is checked against the caller-supplied algorithms allow-list, but signature verification is performed with the algorithm bound to the PyJWK object instead of the header algorithm. An attacker who controls a registered JWK/JWKS private key can sign with a disallowed algorithm, advertise an allowed algorithm in the JWT header, and still be accepted. The issue affects the documented PyJWKClient.get_signing_key_from_jwt(...) flow. This vulnerability is fixed in 2.13.0.