PYSEC-2026-4356

    Dashboard / Vulnerabilities / PYSEC-2026-4356

    PYSEC-2026-4356

    Published: 22 Oct 2026Last Modified: 30 Oct 2026

    Summary:

    Details: Authlib is a Python library which builds OAuth and OpenID Connect servers. Prior to 1.9.1, Authlib's OctKey.import_key() and HMAC signing and verification path accept zero-length key material. If an application's secret lookup can return an empty string or empty bytes, a remote attacker can compute the deterministic HS256, HS384, or HS512 signature for arbitrary token claims and have Authlib treat the token as authentic. This issue is fixed in version 1.9.1.

    References: https://github.com/authlib/authlib/releases/tag/v1.9.1, https://github.com/authlib/authlib/commit/4ff30db442c70e29486e1982cb0ad37c037f5f4b, https://github.com/authlib/authlib/security/advisories/GHSA-8m4g-j4wp-wgcg

    Affected packages

    Package

    Name: authlib

    Purl: pkg:pypi/authlib

    Affected ranges

    Type: ECOSYSTEM

    Events:

    Introduced- 0
    Fixed -1.9.1

    Affected versions

    0.1

    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