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CVE-2026-40165— authentik: SAML NameID XML Comment Injection Enables Authentication Bypass via Identifier Truncation

Quick assessment

Affected
goauthentik authentik
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.

authentik是authentik开源的一个开源身份提供应用程序。 authentik 2025.12.4及之前版本和2026.2.0-rc1至2026.2.2版本存在安全漏洞，该漏洞源于SAML NameID XML注释注入，可能导致攻击者绕过身份验证获取其他账户访问权限。

CVSS 8.7 · High EPSS 0.50% · P41

Affected Version Matrix 2

VendorProduct Version RangeStatus
goauthentik authentik < 2025.12.5 affected
>= 2026.2.0-rc1, < 2026.2.3 affected
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I. Basic Information for CVE-2026-40165

Vulnerability Information
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Vulnerability Title
authentik: SAML NameID XML Comment Injection Enables Authentication Bypass via Identifier Truncation
Source: CVE Program / CVE List V5
Vulnerability Description
authentik is an open-source identity provider. Versions 2025.12.4 and prior, and versions 2026.2.0-rc1 through 2026.2.2 were vulnerable to Authentication Bypass through SAML NameID XML Comment Injection. Due to how authentik extracted the NameID value from a SAML assertion, it was possible for an attacker to trick authentik into only seeing a part of the NameID value, potentially allowing an attacker to gain access to other accounts. This issue could be exploited on an authentik instance with a SAML Source, where the attacker had an account on the SAML Source and the ability to modify their NameID value (commonly username or E-mail), and XML Signing was enabled. The attacker could modify the SAML assertion given to authentik by injecting a comment within the NameID value, which effectively truncated the NameID value to the snippet before the comment, and gave the attacker access to any user account. This issue has been fixed in versions 2025.12.5 and 2026.2.3.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/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
Vulnerability Title
authentik 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
authentik是authentik开源的一个开源身份提供应用程序。 authentik 2025.12.4及之前版本和2026.2.0-rc1至2026.2.2版本存在安全漏洞，该漏洞源于SAML NameID XML注释注入，可能导致攻击者绕过身份验证获取其他账户访问权限。
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

Vendor Product Affected Versions CPE Subscribe
goauthentik authentik < 2025.12.5 -

II. Public POCs for CVE-2026-40165

# POC Description Source Link Shenlong Link
AI-Generated POC Premium
Qwen3.6-35B-A3B · 7798 chars
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III. Intelligence Information for CVE-2026-40165

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Patches & Fixes for CVE-2026-40165 (1)

Vendor Advisories for CVE-2026-40165 (1)

Vendor Pages for CVE-2026-40165 (1)

IV. Related Vulnerabilities

Same product: authentik
Same vendor: goauthentik
Same weakness: CWE-287

V. Comments for CVE-2026-40165

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