authentik: Account Takeover via SAML NameID Comment Truncation
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Attack requirements
- Present
- Impact type
- —
- Confidentiality · integrity · availability
- High · High · None
- Fix status
- Fixed
Attack profile from CVSS 4.0 · CNA. Fix status from CNA.
Summary
authentik is an open-source identity provider. Prior to 2026.2.6 and 2026.5.5, an inbound SAML Source configured with the non-default USERNAME_LINK or EMAIL_LINK user-matching mode interprets an XML comment in a NameID differently from the identity provider's signed assertion. An attacker with an account on the source identity provider who can set the account's NameID can inject an XML comment that truncates the value used by authentik to the text before the comment while the signed assertion remains valid. A crafted NameID can therefore truncate to a victim's username or email and bind the attacker's external identity to the victim's existing account. This grants full takeover without the victim's password or the identity provider's private key, and the malicious link persists so later logins succeed without the comment. Sources using the default unique-identifier matching mode and authentik's outbound SAML Provider role are not affected. This issue is fixed in versions 2026.2.6 and 2026.5.5.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- Yes
- 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 2026.2.6; 2026.5.0 to before 2026.5.5 | 2026.2.6, 2026.5.5 | Patch available | CNA |
- authentik Vendorgoauthentik Affected before 2026.2.6; 2026.5.0 to before 2026.5.5 Fixed in 2026.2.6, 2026.5.5 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 2026.2.6, 2026.5.5
Timeline
- 2026-10-02 Threatist record created from CVE-2026-57580
References
Other 7
- https://github.com/goauthentik/authentik/security/advisories/GHSA-35v6-hv2g-6992
- https://github.com/goauthentik/authentik/pull/24057
- https://github.com/goauthentik/authentik/pull/24062
- https://github.com/goauthentik/authentik/commit/6bd00f09f1f6b5bc5212a10340418fa1b264f02c
- https://github.com/goauthentik/authentik/commit/8704a1b89d7bf46bcef0d3c434c821b937fdecc3
- https://github.com/goauthentik/authentik/releases/tag/version/2026.2.6
- https://github.com/goauthentik/authentik/releases/tag/version/2026.5.5
More goauthentik vulnerabilities
- 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-2024-25628 Insufficient access control for OAuth2 Device Code flow in authentik CVSS 3.1CRITICAL 9.8
- TI-2023-24876 authentik potential installation takeover when default admin user is deleted CVSS 3.1CRITICAL 9.8
Sources
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences