UBUNTU-CVE-2025-59420

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    UBUNTU-CVE-2025-59420

    Published: 22 Sept 2025Last Modified: 16 Jul 2026
    Upstream:
    CVE-2025-59420
    Aliases:
    USN-8065-1

    Summary:

    Details: Authlib is a Python library which builds OAuth and OpenID Connect servers. Prior to version 1.6.4, Authlib’s JWS verification accepts tokens that declare unknown critical header parameters (crit), violating RFC 7515 “must‑understand” semantics. An attacker can craft a signed token with a critical header (for example, bork or cnf) that strict verifiers reject but Authlib accepts. In mixed‑language fleets, this enables split‑brain verification and can lead to policy bypass, replay, or privilege escalation. This issue has been patched in version 1.6.4.

    References: https://ubuntu.com/security/CVE-2025-59420, https://www.cve.org/CVERecord?id=CVE-2025-59420, https://github.com/authlib/authlib/commit/6b1813e4392eb7c168c276099ff7783b176479df, https://github.com/authlib/authlib/security/advisories/GHSA-9ggr-2464-2j32, https://ubuntu.com/security/notices/USN-8065-1

    Affected packages

    Package

    Name: python-authlib

    Purl: pkg:deb/ubuntu/python-authlib?arch=source&distro=esm-apps%2Fjammy

    Affected ranges

    Type: ECOSYSTEM

    Events:

    Introduced- 0
    Fixed -0.15.5-1ubuntu0.1~esm1

    Affected versions

    0.15.4-1
    0.15.5-1

    Common Vulnerability Scoring System

    Attack Vector
    Network
    Adjacent
    Local
    Physical
    Privileges Required
    None
    Low
    High
    User Interaction
    None
    Required
    Scope
    Unchanged
    Changed
    Confidentiality
    None
    Low
    High
    Integrity
    None
    Low
    High
    Availability
    None
    Low
    High
    UBUNTU-CVE-2025-59420 | CVE-DB