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CVE-2026-28498 - Vulnerability Analysis

HighCVSS: 7.5

Last Updated: March 17, 2026

Authlib - Authentication Bypass

Published: March 16, 2026Updated: March 17, 2026PoC AvailableRemote Exploitable

Overview

Authlib Python library < 1.6.9 contains a broken authentication caused by fail-open hash verification logic for at_hash and c_hash claims in OpenID Connect ID Tokens, letting attackers bypass integrity checks by using unsupported alg values, exploit requires crafted forged ID Token.

Severity & Score

Severity: High

CVSS Score: 7.5

Impact

Attackers can bypass token integrity checks, potentially allowing unauthorized access or impersonation.

Mitigation

Upgrade to version 1.6.9 or later.

References

https://github.com/authlib/authlib/commit/b9bb2b25bf8b7e01512d847a95c1749646eaa72b
https://github.com/authlib/authlib/releases/tag/v1.6.9
https://github.com/authlib/authlib/security/advisories/GHSA-m344-f55w-2m6j

Related Resources

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Details

CVE ID: CVE-2026-28498
Severity: High
CVSS Score: 7.5
Type: broken_authentication
Status: confirmed

CWE

CWE-354

CVSS Metrics

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N