What’s Vulnerable › Vulnerabilities
CVE-2026-114616: Authlib accepts an empty HMAC key, allowing JWS/JWT signature forgery (HS256/HS384/HS512)
- Severity: critical (CVSS 9.1 v3.1)
- Exploited in the wild: not listed in CISA KEV
- EPSS: 0.2% probability of exploitation in the next 30 days
- Public exploit or detection template: yes
- Published: 2026-10-22 · updated 2026-10-30
- Weakness: CWE-287
Description
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.
Affected products
How to fix
Upgrade to a fixed version: authlib 1.9.1. Check the vendor advisory for mitigations.
References
- https://github.com/authlib/authlib/commit/4ff30db442c70e29486e1982cb0ad37c037f5f4b
- https://github.com/authlib/authlib/releases/tag/v1.9.1
- https://github.com/authlib/authlib/security/advisories/GHSA-8m4g-j4wp-wgcg
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