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.
Metrics
Affected Vendors & Products
References
History
Tue, 18 Aug 2026 19:15:00 +0000
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Goauthentik
Goauthentik authentik |
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Goauthentik
Goauthentik authentik |
Tue, 18 Aug 2026 18:30:00 +0000
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ssvc
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Tue, 18 Aug 2026 17:15:00 +0000
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| Description | 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. | |
| Title | authentik: Account Takeover via SAML NameID Comment Truncation | |
| Weaknesses | CWE-436 | |
| References |
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| Metrics |
cvssV4_0
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Status: PUBLISHED
Assigner: GitHub_M
Published:
Updated: 2026-08-18T17:45:24.521Z
Reserved: 2026-06-24T18:49:56.208Z
Link: CVE-2026-57580
Updated: 2026-08-18T17:39:58.012Z
Status : Received
Published: 2026-08-18T17:16:59.667
Modified: 2026-08-18T18:18:38.730
Link: CVE-2026-57580
No data.
OpenCVE Enrichment
Updated: 2026-08-18T19:00:12Z