CVE-2026-114615
Authlib incomplete algorithm-confusion fix permits HMAC forgery with prefixed public keys
Impact
Authlib is a Python library which builds OAuth and OpenID Connect servers. From 1.3.1 until 1.9.0, OctKey.import_key() checks asymmetric-key markers only at byte zero while Authlib's PEM loaders accept leading whitespace, comments, or a byte-order mark. In deployments that use the documented mixed algorithm registry and already configure verification with PEM or certificate bytes containing such a prefix, an unauthenticated attacker who knows those same public-key bytes can use them as an HMAC secret and forge HS256 tokens with arbitrary identity or authorization claims. This is a bypass of the remediation for CVE-2024-37568. The module-level jwt object reaches OctKey.import_key() in authlib/jose/rfc7518/oct_key.py, where POSSIBLE_UNSAFE_KEYS fails to identify prefixed asymmetric key material. This issue is fixed in version 1.9.0.
Affected packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| pip | authlib | >= 1.3.1, <= 1.8.0 | 1.9.0 |
Affected products
| Vendor | Product | Affected versions |
|---|---|---|
| Authlib | Authlib | from 1.3.1 before 1.9.0 |
Weakness classification
References
- NVD record
- CVE.org record
- GitHub advisory
- https://github.com/advisories/GHSA-7vr2-2fgp-9w7p
- https://github.com/authlib/authlib/security/advisories/GHSA-7vr2-2fgp-9w7p
- https://nvd.nist.gov/vuln/detail/CVE-2026-114615
- https://github.com/authlib/authlib/pull/945
- https://github.com/authlib/authlib/commit/e3bd41cb29dcfee434453b135ffb487884baeedf
- https://github.com/authlib/authlib/releases/tag/v1.9.0