Authlib is a Python library which builds OAuth and OpenID Connect servers

Why it is Yellow

• CVSS 7.4 high
• Remotely exploitable without logging in
• On your watchlist: python

References

• https://github.com/authlib/authlib/commit/e3bd41cb29dcfee434453b135ffb487884baeedf
• https://github.com/authlib/authlib/pull/945
• https://github.com/authlib/authlib/releases/tag/v1.9.0
• https://github.com/authlib/authlib/security/advisories/GHSA-7vr2-2fgp-9w7p

Original description

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.