TI-2026-28980 Aliases CVE-2026-40165

authentik: SAML NameID XML Comment Injection Enables Authentication Bypass via Identifier Truncation

MEDIUM 40CWE-287Published 2026-05-20 · Updated 2026-05-21

Key facts

Attack vector: Network
Privileges required: None
User interaction: None
Attack complexity: High
Impact type: Security bypass
Confidentiality · integrity · availability: High · High · None
Fix status: Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA. Impact type from CWE-287.

Summary

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV

EPSS 0.00502 43rd percentileScored 2026-11-07

Fix Fixed authentik (goauthentik): 2025.12.5, 2026.2.3

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: None
Automatable: No
Technical impact: Total

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
goauthentik	authentik	before 2025.12.5; 2026.2.0-rc1 to before 2026.2.3	2025.12.5, 2026.2.3	Patch available	CNA

authentik Vendorgoauthentik Affected before 2025.12.5; 2026.2.0-rc1 to before 2026.2.3 Fixed in 2025.12.5, 2026.2.3 Patch available CNA

CPE names Threatist (inferred) · 1

Inferred from how NVD named this product before; not given by a source.

CPE	Versions	Role	Vendor
cpe:2.3:a:goauthentik:authentik::::::::	—	—	goauthentik

cpe:2.3:a:goauthentik:authentik:*:*:*:*:*:*:*:* Versions — — ·goauthentik

Remediation

Fix · CNA authentik (goauthentik) Fixed in 2025.12.5, 2026.2.3

Timeline

2026-10-02 Threatist record created from CVE-2026-40165
2026-10-25 EPSS moved to the below the 50th percentile

References

Other 3

TI-2026-36603 authentik: SourceStage bypass via empty POST CVSS 3.1CRITICAL 9.8
TI-2022-07608 authentik vulnerable to Improper Authentication via invitation URL token reuse CVSS 3.1CRITICAL 9.4
TI-2026-36598 authentik: `UserSourceConnection.user` and `GroupSourceConnection.group` are changeable through the API CVSS 3.1HIGH 8.8
TI-2022-22816 authentik allows existing authenticated users to create arbitrary accounts CVSS 3.1MEDIUM 6.4
TI-2026-41431 authentik: Account Takeover via SAML NameID Comment Truncation CVSS 4.0CRITICAL 9.4
TI-2024-25628 Insufficient access control for OAuth2 Device Code flow in authentik CVSS 3.1CRITICAL 9.8

See all 44 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences