Recommended action window: Monitor and triage in normal cycle
NVD 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.
Priority
LOW
Exploitation
NONE
PoC
NONE
Patch
NONE
Momentum
NONE
🚨HIGH - Authlib JWT Signature Forgery (CVE-2026-114615 + CVE-2026-114616) Authlib allows HMAC key confusion:Empty secret accepted → deterministic HS256/384/512 forgery, Prefixed PEM/public keys treated as HMAC secrets (bypass of previous fix)Attackers can forge JWTs with arbitrary claims and bypass auth. 👉Affected: authlib < 1.9.1 | Upgrade to 1.9.1