CVE-2026-48526

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

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.

Affected

jpadilla · pyjwt

CVSS v3.1 CNA

7.4 HIGHCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

EPSS

0.43% chance of exploitation in the next 30 days, 36th percentile

Published

2026-05-28

Updated

2026-09-10

Proof-of-concept exploits (1)

• advisories/GHSA-xgmm-8j9v-c9wx

Security advisories

• jpadilla/pyjwt/security/advisories/GHSA-xgmm-8j9v-c9wx

References

• CVE Record
• NVD entry