EXECUTIVE SUMMARY:
CVE-2026-47201 with a CVSS score of 8.5 is a XML Signature Wrapping flaw in authentik's SAML Source ACS endpoint that affects the goauthentik.io package in any version prior to 0.0.0-20260528144335-a370d76d23c7. The vulnerability arises because the ACS handler trusts the XML signature to belong to the entire SAML response, but it only validates the signature against the original assertion while later parsing a separate, attacker‑injected assertion, allowing the signature verification to succeed even though the authentication data has been swapped. An attacker who can obtain a legitimate signed SAML response from the upstream Identity Provider—typically by logging in with any valid IdP account—can capture that response, embed a forged assertion containing a victim’s identifier or custom attributes, and replay the modified response to the ACS endpoint; no additional network privileges beyond normal web access are required. Successful exploitation lets the adversary authenticate as an arbitrary federated user or as a local user when email/username matching is enabled, granting unauthorized access to protected applications and data. Exploitation is contingent on the deployment using a SAML Source with signed assertions or signed responses, and on the attacker’s ability to intercept or retrieve a legitimate signed SAML response from the IdP.[/subscribe_to_unlock_form]
EXECUTIVE SUMMARY:
CVE-2026-47201 with a CVSS score of 8.5 is a XML Signature Wrapping flaw in authentik's SAML Source ACS endpoint that affects the goauthentik.io package in any version prior to 0.0.0-20260528144335-a370d76d23c7. The vulnerability arises because the ACS handler trusts the XML signature to belong to the entire SAML response, but it only validates the signature against the original assertion while later parsing a separate, attacker‑injected assertion, allowing the signature verification to succeed even though the authentication data has been swapped. An attacker who can obtain a legitimate signed SAML response from the upstream Identity Provider—typically by logging in with any valid IdP account—can capture that response, embed a forged assertion containing a victim’s identifier or custom attributes, and replay the modified response to the ACS endpoint; no additional network privileges beyond normal web access are required. Successful exploitation lets the adversary authenticate as an arbitrary federated user or as a local user when email/username matching is enabled, granting unauthorized access to protected applications and data. Exploitation is contingent on the deployment using a SAML Source with signed assertions or signed responses, and on the attacker’s ability to intercept or retrieve a legitimate signed SAML response from the IdP.[emaillocker id="1283"]
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REFERENCES:
The following reports contain further technical details:
https://github.com/advisories/GHSA-c3m2-jqmq-pvp3