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CVE-2026-27962— Authlib JWS JWK Header Injection: Signature Verification Bypass

Quick assessment

Affected
authlib authlib
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Authlib是Authlib开源的一个构建 OAuth 和 OpenID Connect 服务器的终极 Python 库。 Authlib 1.6.9之前版本存在数据伪造问题漏洞，该漏洞源于JWS实现中存在JWK标头注入，可能导致未经身份验证的攻击者伪造通过签名验证的任意JWT令牌。

CVSS 9.1 · Critical EPSS 0.52% · P42

Affected Version Matrix 1

VendorProduct Version RangeStatus
authlib authlib < 1.6.9 affected
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I. Basic Information for CVE-2026-27962

Vulnerability Information
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Vulnerability Title
Authlib JWS JWK Header Injection: Signature Verification Bypass
Source: CVE Program / CVE List V5
Vulnerability Description
Authlib is a Python library which builds OAuth and OpenID Connect servers. Prior to version 1.6.9, a JWK Header Injection vulnerability in authlib's JWS implementation allows an unauthenticated attacker to forge arbitrary JWT tokens that pass signature verification. When key=None is passed to any JWS deserialization function, the library extracts and uses the cryptographic key embedded in the attacker-controlled JWT jwk header field. An attacker can sign a token with their own private key, embed the matching public key in the header, and have the server accept the forged token as cryptographically valid — bypassing authentication and authorization entirely. This issue has been patched in version 1.6.9.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
密码学签名的验证不恰当
Source: CVE Program / CVE List V5
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 1.6.9之前版本存在数据伪造问题漏洞，该漏洞源于JWS实现中存在JWK标头注入，可能导致未经身份验证的攻击者伪造通过签名验证的任意JWT令牌。
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)

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Affected Products

Vendor Product Affected Versions CPE Subscribe
authlib authlib < 1.6.9 -

II. Public POCs for CVE-2026-27962

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Qwen3.6-35B-A3B · 8071 chars
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III. Intelligence Information for CVE-2026-27962

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Patches & Fixes for CVE-2026-27962 (1)

Vendor Advisories for CVE-2026-27962 (1)

Vendor Pages for CVE-2026-27962 (1)

Same Patch Batch · authlib · 2026-03-16 · 3 CVEs total

CVE-2026-28498 8.2 HIGH Authlib: Fail-Open Cryptographic Verification in OIDC Hash Binding
CVE-2026-28490 Authlib Vulnerable to JWE RSA1_5 Bleichenbacher Padding Oracle

IV. Related Vulnerabilities

Same product: authlib
Same vendor: authlib
Same weakness: CWE-347

V. Comments for CVE-2026-27962

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