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Untriaged
Permalink CVE-2026-57580
9.4 CRITICAL
  • CVSS version (CVSS): 4.0
  • Attack Vector (AV): Network (N)
  • Attack Complexity (AC): Low (L)
  • Attack Requirement (AT): Present (P)
  • Privileges Required (PR): None (N)
  • User Interaction (UI): None (N)
  • Vulnerable System Impact Confidentiality (VC): High (H)
  • Vulnerable System Impact Integrity (VI): High (H)
  • Vulnerable System Impact Availability (VA): None (N)
  • Subsequent System Impact Confidentiality (SC): High (H)
  • Subsequent System Impact Integrity (SI): High (H)
  • Subsequent System Impact Availability (SA): None (N)
  • Modified Attack Vector (MAV): Network (N)
  • Modified Attack Complexity (MAC): Low (L)
  • Modified Attack Requirement (MAT): Present (P)
  • Modified Privileges Required (MPR): None (N)
  • Modified User Interaction (MUI): None (N)
  • Modified Vulnerable System Impact Confidentiality (MVC): High (H)
  • Modified Vulnerable System Impact Integrity (MVI): High (H)
  • Modified Vulnerable System Impact Availability (MVA): None (N)
  • Modified Subsequent System Impact Confidentiality (MSC): High (H)
  • Modified Subsequent System Impact Integrity (MSI): High (H)
  • Modified Subsequent System Impact Availability (MSA): Negligible (N)
  • Safety (S): Not Defined (X)
  • Automatable (AU): Not Defined (X)
  • Recovery (R): Not Defined (X)
  • Value Density (V): Not Defined (X)
  • Vulnerability Response Effort (RE): Not Defined (X)
  • Provider Urgency (U): Not Defined (X)
  • Confidentiality Req. (CR): Not Defined (X)
  • Integrity Req. (IR): Not Defined (X)
  • Availability Req. (AR): Not Defined (X)
  • Exploit Maturity (E): Not Defined (X)
created 4 weeks ago Activity log
  • Created suggestion 4 weeks ago
authentik: Account Takeover via SAML NameID Comment Truncation

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.

Affected products

authentik
  • ==>= 2026.5.0, < 2026.5.5
  • ==< 2026.2.6

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