CVE-2026-4868: Authorization Bypass Through User-Controlled Key in GitLab

Synopsis

An authorization bypass vulnerability in GitLab EE allows an authenticated attacker to hijack Duo AI workflow execution under another user's identity. The vulnerability is reachable over the network, requires a low-privilege account, and exploits improper user identity resolution when triggering Duo AI workflow runners. Successful exploitation gives the attacker read and write access scoped to the impersonated user's permissions, without that user's knowledge. A patched-image rebuild at versions 18.10.7, 18.11.4, and 19.0.1 is available on HarborGuard for affected environments.

HarborGuard Coverage

Exploit Conditions

• Network reachabilityRequired

  The attacker must reach the GitLab EE service over the network to trigger the Duo AI workflow runner endpoint.

• AuthenticationRequired

  A valid GitLab account is required; any low-privilege user account is sufficient to attempt the identity-resolution bypass.

• Victim interactionNot required

  No action from the impersonated user or any other party is needed to complete the attack.

• Attack complexityDetail

  Exploitation is rated High complexity, meaning specific conditions in the environment or timing must align for the identity resolution flaw to be triggered reliably.

Blast Radius

• The attacker reads repository contents, issues, merge requests, and other data accessible to the impersonated user.
• The attacker writes on behalf of the impersonated user, including creating commits, approving merge requests, or modifying project settings within that user's permission scope.
• Because the scope is Changed (S:C), impact can extend beyond the attacker's own GitLab account into projects and groups the victim user has access to.
• No availability impact is introduced; the service continues running while the unauthorized access occurs silently.