Not Failing Securely ('Failing Open') Affecting authlib package, versions [,1.6.9)
Threat Intelligence
Snyk has a proof-of-concept or detailed explanation of how to exploit this vulnerability.
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-PYTHON-AUTHLIB-15674453
- published17 Mar 2026
- disclosed16 Mar 2026
- creditJay Neiva, Pr00fOf3xpl0it
Introduced: 16 Mar 2026
CVE-2026-28498 (opens in a new tab)How to fix?
Upgrade authlib to version 1.6.9 or higher.
Overview
authlib is a library in building OAuth and OpenID Connect servers.
Affected versions of this package are vulnerable to Not Failing Securely ('Failing Open') via the _verify_hash function in authlib/oidc/core/claims.py. An attacker can substitute an access token or authorization code undetected by supplying an ID token with an unsupported alg header, causing create_half_hash to return None and the verification to incorrectly succeed.