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CVE-2026-114616— Authlib accepts an empty HMAC key, allowing JWS/JWT signature forgery (HS256/HS384/HS512)

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 1.9.1 版本之前，Authlib 的 OctKey.import_key() 方法以及 HMAC 签名与验证路径会接受零长度的密钥材料。如果应用程序的密钥查找逻辑可能返回空字符串或空字节，远程攻击者即可针对任意令牌声明计算出确定性的 HS256、HS384 或 HS512 签名，并诱使 Authlib 将该令牌视为合法。该问题已在 1.9.1 版本中修复。

CVSS 7.4 · High
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I. Basic Information for CVE-2026-114616

Vulnerability Information
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Vulnerability Title
Authlib accepts an empty HMAC key, allowing JWS/JWT signature forgery (HS256/HS384/HS512)
Source: CVE Program / CVE List V5
Vulnerability Description
Authlib is a Python library which builds OAuth and OpenID Connect servers. Prior to 1.9.1, Authlib's OctKey.import_key() and HMAC signing and verification path accept zero-length key material. If an application's secret lookup can return an empty string or empty bytes, a remote attacker can compute the deterministic HS256, HS384, or HS512 signature for arbitrary token claims and have Authlib treat the token as authentic. This issue is fixed in version 1.9.1.
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
认证机制不恰当
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
authlib authlib < 1.9.1 -

II. Public POCs for CVE-2026-114616

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III. Intelligence Information for CVE-2026-114616

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Other References for CVE-2026-114616 (3)

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

CVE-2026-114615 7.4 HIGH Authlib incomplete algorithm-confusion fix permits HMAC forgery with prefixed public keys
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-287

V. Comments for CVE-2026-114616

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