CVE-2026-49852

joserfc is a Python library that provides an implementation of several JSON Object Signing and Encryption (JOSE) standards. Prior to 1.6.8, joserfc.jwt.decode accepts attacker-forged HMAC-signed tokens when the caller-supplied verification key is the empty string or None, because HMACAlgorithm.sign and HMACAlgorithm.verify in src/joserfc/_rfc7518/jws_algs.py pass the output of OctKey.get_op_key(...) to hmac.new(...) and OctKey.import_key in src/joserfc/_rfc7518/oct_key.py only emits a SecurityWarning for keys shorter than 14 bytes without rejecting zero-length input. This issue is fixed in version 1.6.8.

Score

CVSS 4.0 8.7 High

Status

Deferred - security-advisories@github.com

Published

2026-07-17

Last modified

2026-10-24

Weaknesses

CWE-1391, CWE-287, CWE-326

Affected products

• Joserfc (Authlib)

References

• https://github.com/authlib/joserfc/security/advisories/GHSA-gg9x-qcx2-xmrh
• https://github.com/authlib/joserfc/commit/86d00910b2b2d2d07503fee9b572906daefab7f1
• https://github.com/authlib/joserfc/releases/tag/1.6.8