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PyJWT: Public-key JWK accepted as HMAC secret enables forged HS256 tokens when mixed families are allowed

jpadilla pyjwt · CVE-2026-48526
0 news outlets0 CERTs and agencies0 researchers

Assessment: Track

SSVC decision points: exploitation poc, automatable no, technical impact total, deployment low.

What is it?

PyJWT is a JSON Web Token implementation in Python. Prior to 2.13.0, when the verifier is decoding JSON Web Tokens, while supporting both asymmetric and HMAC algorithms, the library does not validate use of JSON Web Keys in HMAC algorithm, allowing attacker to use the issuer public key as the secret key for HMAC algorithm. This vulnerability is fixed in 2.13.0.

Evidence

No coverage recorded yet.

Exploitation

  • Public proof of concept
  • Exploited in the wild
  • Listed as known exploited
CVSS
7.4
EPSS
0.4%
First seen
1 d ago
Status
corroborated

All jpadilla vulnerabilities