Debian alert DLA-4708-1 (python-authlib)

From:
             
 
Andrej Shadura <andrewsh@debian.org>
To:
             
 
debian-lts-announce@lists.debian.org
Subject:
             
 
[SECURITY] [DLA 4708-1] python-authlib security update
Date:
             
 
Fri, 31 Jul 2026 17:46:59 +0200
Message-ID:
             
 
<20260731154700.1049254-1-andrewsh@debian.org>
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Debian LTS Advisory DLA-4708-1                debian-lts@lists.debian.org
https://www.debian.org/lts/security/                       Andrej Shadura
July 31, 2026                                 https://wiki.debian.org/LTS
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Package        : python-authlib
Version        : 0.15.4-1+deb11u4 1.2.0-1+deb12u2
CVE ID         : CVE-2026-27962 CVE-2026-28490 CVE-2026-28498 CVE-2026-41425 
                 CVE-2026-44681

The following security issue has been identified (and fixed) in python-authlib
as shipped in Debian bullseye and Debian bookworm.

CVE-2026-44681

    An unauthenticated open redirect in Authlib's OpenIDImplicitGrant
    and OpenIDHybridGrant authorisation endpoint allowed a remote
    attacker to cause the authorisation server to issue an HTTP 302 to
    an attacker-chosen URL by submitting an authorisation request that
    omits the openid scope.

For Debian 11 bullseye, this problem has been fixed in version
0.15.4-1+deb11u4.

In addition, the following issues have been fixed in the python-authlib version
as shipped in Debian bookworm:

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
    deserialisation 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.

CVE-2026-41425

    CSRF protection now covers the cache feature in
    authlib.integrations.starlette_client.OAuth as well.

For Debian 12 bookworm, these problems have been fixed in version
1.2.0-1+deb12u2.

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
these updates to your system and frequently asked questions can be
found at: https://wiki.debian.org/LTS
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