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

- 種別: advisory
- 重大度: high
- 関連技術: python
- CVE: CVE-2026-114616
- 公開日時: 2026-10-27T16:09:22.000Z
- 情報源: GitHub Advisory Database (https://github.com/advisories/GHSA-8m4g-j4wp-wgcg)
- パーマリンク: https://vulnpulse.app/items/ghsa-ghsa-8m4g-j4wp-wgcg

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…