FKIE_CVE-2026-57580

Vulnerability from fkie_nvd - Published: 2026-08-18 17:16 - Updated: 2026-08-18 18:18
Severity
9.4 (Critical) - CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:H/SI:H/SA:N
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.
References
security-advisories@github.comhttps://github.com/goauthentik/authentik/commit/6bd00f09f1f6b5bc5212a10340418fa1b264f02c
security-advisories@github.comhttps://github.com/goauthentik/authentik/commit/8704a1b89d7bf46bcef0d3c434c821b937fdecc3
security-advisories@github.comhttps://github.com/goauthentik/authentik/pull/24057
security-advisories@github.comhttps://github.com/goauthentik/authentik/pull/24062
security-advisories@github.comhttps://github.com/goauthentik/authentik/releases/tag/version/2026.2.6
security-advisories@github.comhttps://github.com/goauthentik/authentik/releases/tag/version/2026.5.5
security-advisories@github.comhttps://github.com/goauthentik/authentik/security/advisories/GHSA-35v6-hv2g-6992
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "product": "authentik",
          "vendor": "goauthentik",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 2026.2.6"
            },
            {
              "status": "affected",
              "version": "\u003e= 2026.5.0, \u003c 2026.5.5"
            }
          ]
        }
      ],
      "source": "security-advisories@github.com"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "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\u0027s signed assertion. An attacker with an account on the source identity provider who can set the account\u0027s 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\u0027s username or email and bind the attacker\u0027s external identity to the victim\u0027s existing account. This grants full takeover without the victim\u0027s password or the identity provider\u0027s private key, and the malicious link persists so later logins succeed without the comment. Sources using the default unique-identifier matching mode and authentik\u0027s outbound SAML Provider role are not affected. This issue is fixed in versions 2026.2.6 and 2026.5.5."
    }
  ],
  "id": "CVE-2026-57580",
  "lastModified": "2026-08-18T18:18:38.730",
  "metrics": {
    "cvssMetricV40": [
      {
        "cvssData": {
          "Automatable": "NOT_DEFINED",
          "Recovery": "NOT_DEFINED",
          "Safety": "NOT_DEFINED",
          "attackComplexity": "LOW",
          "attackRequirements": "PRESENT",
          "attackVector": "NETWORK",
          "availabilityRequirement": "NOT_DEFINED",
          "baseScore": 9.4,
          "baseSeverity": "CRITICAL",
          "confidentialityRequirement": "NOT_DEFINED",
          "exploitMaturity": "NOT_DEFINED",
          "integrityRequirement": "NOT_DEFINED",
          "modifiedAttackComplexity": "NOT_DEFINED",
          "modifiedAttackRequirements": "NOT_DEFINED",
          "modifiedAttackVector": "NOT_DEFINED",
          "modifiedPrivilegesRequired": "NOT_DEFINED",
          "modifiedSubAvailabilityImpact": "NOT_DEFINED",
          "modifiedSubConfidentialityImpact": "NOT_DEFINED",
          "modifiedSubIntegrityImpact": "NOT_DEFINED",
          "modifiedUserInteraction": "NOT_DEFINED",
          "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
          "modifiedVulnConfidentialityImpact": "NOT_DEFINED",
          "modifiedVulnIntegrityImpact": "NOT_DEFINED",
          "privilegesRequired": "NONE",
          "providerUrgency": "NOT_DEFINED",
          "subAvailabilityImpact": "NONE",
          "subConfidentialityImpact": "HIGH",
          "subIntegrityImpact": "HIGH",
          "userInteraction": "NONE",
          "valueDensity": "NOT_DEFINED",
          "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:H/SI:H/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
          "version": "4.0",
          "vulnAvailabilityImpact": "NONE",
          "vulnConfidentialityImpact": "HIGH",
          "vulnIntegrityImpact": "HIGH",
          "vulnerabilityResponseEffort": "NOT_DEFINED"
        },
        "source": "security-advisories@github.com",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-57580",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "total"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-08-18T17:45:20.895315Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-08-18T17:16:59.667",
  "references": [
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/goauthentik/authentik/commit/6bd00f09f1f6b5bc5212a10340418fa1b264f02c"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/goauthentik/authentik/commit/8704a1b89d7bf46bcef0d3c434c821b937fdecc3"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/goauthentik/authentik/pull/24057"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/goauthentik/authentik/pull/24062"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/goauthentik/authentik/releases/tag/version/2026.2.6"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/goauthentik/authentik/releases/tag/version/2026.5.5"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/goauthentik/authentik/security/advisories/GHSA-35v6-hv2g-6992"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Received",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-436"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Secondary"
    }
  ]
}



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