CVE-2026-48523
MEDIUM
MEDIUM
Priority: 0.01
BB Relevance:
61/100
Published: 2026-05-28
Modified: 2026-10-25
First seen: 2026-10-29
Status: active
Attack Surface
Network
Low Complexity
No Interaction
CVSS Vector Breakdown
AV:
Network
AC:
Low
PR:
Low
UI:
None
S:
Unchanged
C:
Low
I:
Low
A:
None
Description
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.
Weakness Classification (1)
Affected Software (1)
| Vendor | Product | Version |
|---|---|---|
| pyjwt_project | pyjwt | 2.9.0 – 2.13.0 |
References & Advisories (1)
Exploit
Vendor Advisory