SB20261109174 - Incomplete List of Disallowed Inputs in authlib

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Main Vulnerability Database SB20261109174

SB20261109174 - Incomplete List of Disallowed Inputs in authlib

Published: November 9, 2026

Security Bulletin ID SB20261109174
CSH Severity
Medium
Patch available
YES
Number of vulnerabilities 1
Exploitation vector Remote access
Highest impact Data manipulation

Breakdown by Severity

Medium 100%
  • Low
  • Medium
  • High
  • Critical

Description

This security bulletin contains information about 1 vulnerability.


1) Incomplete List of Disallowed Inputs (CVE-ID: N/A)

CWE-ID: CWE-184 - Incomplete List of Disallowed Inputs

CVSSv4: 9.1 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N]


The vulnerability allows an unauthenticated remote attacker to forge JWTs containing arbitrary claims.

The vulnerability exists due to incomplete public-key rejection in authlib's JOSE component, which accepts tab-separated OpenSSH public keys and OpenSSH certificates as HMAC secrets. An unauthenticated remote attacker who knows the public key can sign accepted HS256 tokens when an application passes that key to jwt.decode or JsonWebSignature without restricting algorithms.


Remediation

Install update from vendor's website.

References