Authlib accepts an empty HMAC key, allowing JWS/JWT signature forgery (HS256/HS384/HS512)

影響: pip:Authlib < 1.9.1 → 1.9.1

Reporter: Cavan Loughran, Celvex Group Inc. Summary Authlib's symmetric (oct) key handling accepts an empty key (empty bytes b'' / empty string '') as a valid HMAC signing and verification key. An empty HMAC key produces a deterministic digest that any party can reproduce, so an attacker who knows (or can cause) the application to verify a token with an empty key can forge arbitrary tokens that pass HS256/HS384/HS512 signature verification. This is the Authlib member of the cross-language empty…

Read on GitHub Advisory Database

On 10/28/2026, 01:09 AM, GitHub Advisory Database published "Authlib accepts an empty HMAC key, allowing JWS/JWT signature forgery (HS256/HS384/HS512)" (type: Advisory). Severity is "High" (high). Related technologies: Python. CVE: CVE-2026-114616.