CVE-2025-59420— Authlib: JWS/JWT accepts unknown crit headers (RFC violation → possible authz bypass)
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I. Basic Information for CVE-2025-59420
Vulnerability Information
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Vulnerability Title
Authlib: JWS/JWT accepts unknown crit headers (RFC violation → possible authz bypass)
Source: NVD (National Vulnerability Database)
Vulnerability Description
Authlib is a Python library which builds OAuth and OpenID Connect servers. Prior to version 1.6.4, Authlib’s JWS verification accepts tokens that declare unknown critical header parameters (crit), violating RFC 7515 “must‑understand” semantics. An attacker can craft a signed token with a critical header (for example, bork or cnf) that strict verifiers reject but Authlib accepts. In mixed‑language fleets, this enables split‑brain verification and can lead to policy bypass, replay, or privilege escalation. This issue has been patched in version 1.6.4.
Source: NVD (National Vulnerability Database)
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Source: NVD (National Vulnerability Database)
Vulnerability Type
对数据真实性的验证不充分
Source: NVD (National Vulnerability Database)
Vulnerability Title
Authlib 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Authlib是Authlib开源的一个构建 OAuth 和 OpenID Connect 服务器的终极 Python 库。 Authlib 1.6.4之前版本存在安全漏洞，该漏洞源于JWS验证接受声明未知关键标头参数的令牌，可能导致策略绕过、重放或权限提升。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)
Affected Products
II. Public POCs for CVE-2025-59420
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IV. Related Vulnerabilities
Same product: authlib
- CVE-2026-41425
Authlib: Cross-site request forging when using cache - CVE-2026-28498
Authlib: Fail-Open Cryptographic Verification in OIDC Hash B - CVE-2026-28490
Authlib Vulnerable to JWE RSA1_5 Bleichenbacher Padding Orac - CVE-2026-27962
Authlib JWS JWK Header Injection: Signature Verification Byp - CVE-2026-28802
Authlib: Setting `alg: none` and a blank signature appears t
Same vendor: authlib
- CVE-2026-41425
Authlib: Cross-site request forging when using cache - CVE-2026-28498
Authlib: Fail-Open Cryptographic Verification in OIDC Hash B - CVE-2026-28490
Authlib Vulnerable to JWE RSA1_5 Bleichenbacher Padding Orac - CVE-2026-27962
Authlib JWS JWK Header Injection: Signature Verification Byp - CVE-2026-28802
Authlib: Setting `alg: none` and a blank signature appears t
Same weakness: CWE-345
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Vaultwarden WebAuthn credential metadata tampered before sig - CVE-2026-43534
OpenClaw < 2026.4.10 - Unsanitized External Input in Agent H
V. Comments for CVE-2025-59420
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