CVE-2026-54730: authentik: Authentication Flow Bypass via Unguarded challenge_valid() in AuthenticatorEndpointGDTCStage and GoogleChromeStageView

Vulnerability summary

CVE-2026-54730 is a high (CVSS 8.6) Improper Access Control vulnerability in goauthentik authentik. EPSS estimates a 0.68% chance of exploitation in the next 30 days, higher than 52.4% of scored vulnerabilities.

Timeline

1. 18-08-2026
   PublishedVulnerability first disclosed.
2. 18-08-2026
   Last modifiedVulnerability information updated.

Description

authentik is an open-source identity provider. Prior to 2026.2.6 and 2026.5.5, the enterprise Google Chrome device-trust stages advance the flow without confirming that the out-of-band device attestation actually ran. Affected enterprise deployments place either a Google Chrome Endpoint stage with mode set to REQUIRED or the deprecated Google Chrome Device Trust Connector stage in an authentication flow. The device attestation occurs in a verification iframe that calls the Google Verified Access API and records the verified device on success, but the vulnerable stages treat the flow as passed as soon as the stage is submitted. An attacker who can reach such a stage, including after primary username and password authentication, can skip the verification iframe and authenticate from a device that was never verified. Where device trust is the only additional factor, that protection is fully bypassed, while other configured factors remain in force. This issue is fixed in versions 2026.2.6 and 2026.5.5.

• CWE-284Improper Access ControlThe product does not restrict or incorrectly restricts access to a resource from an unauthorized actor.
• CWE-807Reliance on Untrusted Inputs in a Security DecisionThe product uses a protection mechanism that relies on the existence or values of an input, but the input can be modified by an untrusted actor in a way that bypasses the protection mechanism.