Is there a public exploit for CVE-2026-28498?

No public exploit for CVE-2026-28498 was found in Exploit-DB, Metasploit, Nuclei templates or public proof-of-concept repositories. That is an absence of evidence rather than proof that none exists.

How severe is CVE-2026-28498?

CVE-2026-28498 scores CVSS 8.2 (v4.0), rated high. EPSS puts the chance of exploitation in the next 30 days at 0.24%.

What does CVE-2026-28498 affect?

CVE-2026-28498 affects authlib authlib.

8.2 High

Authlib is a Python library which builds OAuth and OpenID Connect servers.

CVE-2026-28498

Authlib is a Python library which builds OAuth and OpenID Connect servers. Prior to version 1.6.9, a library-level vulnerability was identified in the Authlib Python library concerning the validation of OpenID Connect (OIDC) ID Tokens. Specifically, the internal hash verification logic (verifyhash) responsible for validating the athash (Access Token Hash) and chash (Authorization Code Hash) claims exhibits a fail-open behavior when encountering an unsupported or unknown cryptographic algorithm. This flaw allows an attacker to bypass mandatory integrity protections by supplying a forged ID Token with a deliberately unrecognized alg header parameter. The library intercepts the unsupported state and silently returns True (validation passed), inherently violating fundamental cryptographic design principles and direct OIDC specifications. This issue has been patched in version 1.6.9.

Assessment

CVSS: 8.2 (v4.0)
Severity: High
EPSS: 0.24% chance of exploitation in the next 30 days
Known exploited: Not listed in CISA KEV
Exploit availability: Nothing found in Exploit-DB, Metasploit, Nuclei or public PoC repositories
Published: 16 March 2026
Last updated: 10 September 2026
Affected: authlib · authlib
Weakness: CWE-325, CWE-354, CWE-573
Assigner: security-advisories@github.com

CVSS vectorCVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N

At the source

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