MyTube is a self-hosted downloader and player for several video websites Prior to version 1.8.72, an unauthenticated attacker can lock out administrator and visitor accounts from password-based authentication by triggering failed login attempts. The application exposes three password verification endpoints, all of which are publicly accessible. All three endpoints share a single file-backed login attempt state stored in login-attempts.json.

When any endpoint records a failed authentication attempt via recordFailedAttempt(), the shared login attempt state is updated, increasing the failedAttempts counter and adjusting the associated timestamps and cooldown values. Before verifying a password, each endpoint calls canAttemptLogin(). This function checks the shared JSON file to determine whether a cooldown period is active.

If the cooldown has not expired, the request is rejected before the password is validated. Because the failed attempt counter and cooldown timer are globally shared, failed authentication attempts against any endpoint affect all other endpoints. An attacker can exploit this by repeatedly sending invalid authentication requests to any of these endpoints, incrementing the shared counter and waiting for the cooldown period between attempts.

By doing so, the attacker can progressively increase the lockout duration until it reaches 24 hours, effectively preventing legitimate users from authenticating. Once the maximum lockout is reached, the attacker can maintain the denial of service indefinitely by waiting for the cooldown to expire and sending another failed attempt, which immediately triggers another 24-hour lockout if no successful login occurred in the meantime. Version 1.8.72 fixes the vulnerability.