# CVE-2026-28498: python-authlib: Authlib is a Python library which builds OAuth and OpenID Connect servers

CVE-2026-28498 is fixed in 3 products on 1 platform, first by python3-authlib 0.15.5-1ubuntu0.1~esm2, released March 16, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-28498
- Priority: High
- CVSS: 7.5 (high)
- EPSS: 0.0024
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Mar 16, 2026

## Description

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 (_verify_hash) responsible for validating the at_hash (Access Token Hash) and c_hash (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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | python-Authlib opensuse-leap 15.6 | 1.3.1-150600.3.17.1 | [SUSE-SU-2026:0975-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-0975-1.md) | Mar 23, 2026 |
| Linux | python-Authlib opensuse-leap 16.0 | 1.5.2-bp160.3.1 | [OPENSUSE-SU-2026:20392-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-20392-1.md) | Mar 18, 2026 |
| Linux | python-Authlib sles 15.6 | 1.3.1-150600.3.17.1 | [SUSE-SU-2026:0975-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-0975-1.md) | Mar 23, 2026 |
| Linux | python-Authlib sles 15.7 | 1.3.1-150600.3.17.1 | [SUSE-SU-2026:0975-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-0975-1.md) | Mar 23, 2026 |
| Linux | python-authlib Debian 12.15 (bookworm) | 1.2.0-1+deb12u2 | [DEBIAN-CVE-2026-28498](https://patchblox.com/security/data/fix/linux/debian-cve-2026-28498.md) | Mar 16, 2026 |
| Linux | python-authlib Debian 14 | 1.6.9-1 | [DEBIAN-CVE-2026-28498](https://patchblox.com/security/data/fix/linux/debian-cve-2026-28498.md) | Mar 16, 2026 |
| Linux | python3-authlib Ubuntu 22.04.1 LTS (jammy) | 0.15.5-1ubuntu0.1~esm2 | [python3-authlib 0.15.5-1ubuntu0.1~esm2](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-python3-authlib-0.15.5-1ubuntu0.1-esm2.md) | Mar 16, 2026 |
| Linux | python3-authlib Ubuntu 24.04.5 LTS (noble) | 1.3.0-1ubuntu0.1~esm2 | [python3-authlib 1.3.0-1ubuntu0.1~esm2](https://patchblox.com/security/data/fix/linux/ubuntu-noble-python3-authlib-1.3.0-1ubuntu0.1-esm2.md) | Apr 24, 2026 |
| Linux | python3-authlib Ubuntu 26.04.1 LTS (resolute) | 1.6.7-1ubuntu0.1~esm1 | [python3-authlib 1.6.7-1ubuntu0.1~esm1](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-python3-authlib-1.6.7-1ubuntu0.1-esm1.md) | Apr 24, 2026 |

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Data as of 2026-11-08T13:06:02Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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