CVE-2026-114615 - Authlib incomplete algorithm-confusion fix permits HMAC forgery with prefixed public keys

CVE-2026-114615 - Authlib incomplete algorithm-confusion fix permits HMAC forgery with prefixed public keys

https://cvefeed.io/rssfeed/latest.atom / Fri, 10/23/2026 - 02:11
CVE ID :CVE-2026-114615
Published : Oct. 22, 2026, 9:10 p.m. | 1 hour, 11 minutes ago
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.
Severity: 7.4 | HIGH
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