Coolify through 4.3.17 contains an authentication bypass vulnerability in the OAuth callback handler that signs users into existing accounts based solely on email address without verifying provider assertions or binding OAuth identities. Attackers can register a victim's email address on any enabled OAuth provider to obtain authenticated sessions as that user, bypassing password requirements and two-factor authentication.

Coolify versions through 4.3.17 contain a critical authentication bypass vulnerability in the OAuth callback handler. The flaw allows attackers to sign into existing user accounts by registering the victim's email address on any enabled OAuth provider. The system incorrectly matches accounts based solely on email address without verifying provider assertions or binding OAuth identities. This attack vector effectively bypasses both password requirements and two-factor authentication. Any attacker with knowledge of a target's email address can exploit this to gain full authenticated sessions. The vulnerability exists in the OauthController.php handler and associated routing logic. It represents a complete account takeover risk for all users of affected Coolify deployments with OAuth providers enabled.