CVE-2026-28802— Authlib: Setting `alg: none` and a blank signature appears to bypass signature verification
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I. Basic Information for CVE-2026-28802
Vulnerability Information
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Vulnerability Title
Authlib: Setting `alg: none` and a blank signature appears to bypass signature verification
Source: NVD (National Vulnerability Database)
Vulnerability Description
Authlib is a Python library which builds OAuth and OpenID Connect servers. From version 1.6.5 to before version 1.6.7, previous tests involving passing a malicious JWT containing alg: none and an empty signature was passing the signature verification step without any changes to the application code when a failure was expected.. This issue has been patched in version 1.6.7.
Source: NVD (National Vulnerability Database)
CVSS Information
N/A
Source: NVD (National Vulnerability Database)
Vulnerability Type
密码学签名的验证不恰当
Source: NVD (National Vulnerability Database)
Vulnerability Title
Authlib 数据伪造问题漏洞
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 1.6.5至1.6.7之前版本存在数据伪造问题漏洞，该漏洞源于传递包含alg: none和空签名的恶意JWT时通过签名验证步骤，可能导致绕过预期失败。
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-2026-28802
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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-2025-68158
Authlib: 1-click Account Takeover
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-2026-27932
joserfc PBES2 p2c Unbounded Iteration Count enables Denial o
Same weakness: CWE-347
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V. Comments for CVE-2026-28802
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