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

Quick assessment

Affected
authlib authlib
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Authlib 是一个用于构建 OAuth 和 OpenID Connect 服务器的 Python 库。在 1.3.1 至 1.9.0 版本中， 方法仅在字节的第 0 位检查非对称密钥的标识符，而 Authlib 的 PEM 加载器却允许前导空白字符、注释或字节顺序标记（BOM）。在已启用文档中描述的混合算法注册表、且已使用包含此类前缀的 PEM 或证书字节配置验证的部署环境中，任何知晓相同公钥字节的未认证攻击者均可将其用作 HMAC 密钥，从而伪造包含任意身份或授权声明的 HS256 令牌。此问题构成了对 CV

CVSS 7.4 · High
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I. Basic Information for CVE-2026-114615

Vulnerability Information
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Vulnerability Title
Authlib incomplete algorithm-confusion fix permits HMAC forgery with prefixed public keys
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
不完整的黑名单
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
authlib authlib >= 1.3.1, < 1.9.0 -

II. Public POCs for CVE-2026-114615

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III. Intelligence Information for CVE-2026-114615

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Other References for CVE-2026-114615 (4)

Same Patch Batch · authlib · 2026-10-22 · 7 CVEs total

CVE-2026-114616 7.4 HIGH Authlib accepts an empty HMAC key, allowing JWS/JWT signature forgery (HS256/HS384/HS512)
CVE-2026-114618 6.8 MEDIUM Authlib: Default JWT bearer grant accepts assertions for the wrong audience
CVE-2026-114620 5.4 MEDIUM Authlib: Unvalidated request_uri fetch in JWT-secured authorization request (JAR) leading
CVE-2026-114619 4.6 MEDIUM Authlib: OpenID implicit grant checks raw scope instead of allowed scope before issuing ID
CVE-2026-114617 4.2 MEDIUM Authlib: ID token can disable its own nonce validation via the nonce_supported claim
CVE-2026-114614 2.6 LOW Authlib: is_secure_transport() loopback exemption can be bypassed with a userinfo componen

IV. Related Vulnerabilities

Same product: authlib
Same vendor: authlib
Same weakness: CWE-184

V. Comments for CVE-2026-114615

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