Improper Verification of Cryptographic Signature Affecting pyjwt package, versions <2.10.1-4ubuntu1.1


Severity

Recommended
medium

Based on Ubuntu security rating.

Threat Intelligence

EPSS
0.17% (6th percentile)

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  • Snyk IDSNYK-UBUNTU2604-PYJWT-17092856
  • published16 Sept 2026
  • disclosed28 May 2026

Introduced: 28 May 2026

CVE-2026-48523  (opens in a new tab)
CWE-347  (opens in a new tab)

How to fix?

Upgrade Ubuntu:26.04 pyjwt to version 2.10.1-4ubuntu1.1 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream pyjwt package and not the pyjwt package as distributed by Ubuntu. See How to fix? for Ubuntu:26.04 relevant fixed versions and status.

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.

CVSS Base Scores

version 3.1