Debian 11 python-authlib Critical Auth Bypass & Info Leak DLA-4579-1
debian lts
May 11, 2026
Three security vulnerabilities were discovered in python-authlib, a python library which builds OAuth and OpenID Connect servers, that can cause authentication bypass or informatio...
Topics Covered
Summary
CVE-2026-27962
Fix authentication and authorization bypass vulnerability by embedding a
crafted public key in the jwk header field when key=None is passed to JWS
deserialization functions.
CVE-2026-28490
Authlib exposed distinguishable error responses between invalid PKCS#1 v1.5
padding and invalid AES-GCM tag, enabling Bleichenbacher-style attacks.
CVE-2026-28498
Fix OIDC ID Token validation bypass in at_hash and c_hash verification.
_verify_hash() silently returned True when create_half_hash() received an
unknown algorithm, allowing forged ID
Tokens to pass validation.
For Debian 11 bullseye, these problems have been fixed in version
0.15.4-1+deb11u2.
We recommend that you upgrade your python-authlib packages.
For the detailed security status of python-authlib please refer to
its security tracker page at:
https://security-tracker.debian.org/tracker/python-authlib
Further information about Debian LTS security advisories, how to apply
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Package: python-authlib
Version: 0.15.4-1+deb11u2
CVE ID: CVE-2026-27962 CVE-2026-28490 CVE-2026-28498
Topics Covered
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