Attack Chain

1. Attacker obtains a valid session token for any user role (including BASIC) on a migrated Actual server.
2. Attacker sends a POST request to /account/change-password with a new password, using the valid session token in the X-Actual-Token header and a JSON body containing the desired password.
3. The server updates the password hash in the auth table for the inactive password authentication method, due to the missing authorization check.
4. Attacker sends a POST request to /account/login with the loginMethod parameter set to “password” and the password set in the previous step.
5. The server accepts the client-supplied loginMethod and authenticates the attacker as the anonymous admin account (username = ‘’), as this is the default user created during multiuser migration with ADMIN role.
6. The server returns a new session token for the admin account.
7. Attacker uses the admin token to access administrative functions on the server.
8. Attacker can manage all users, access all budget files, modify file access controls, and change server configuration.

Impact

Successful exploitation of this vulnerability grants an attacker full administrative privileges on the affected Actual server. This allows the attacker to manage all users, access all budget files regardless of ownership, modify file access controls, and change server configuration. The vulnerability affects multi-user servers running OpenID Connect that were previously configured with password authentication, meaning that a wide range of sensitive data and configurations are at risk. This can lead to significant data breaches, financial losses, and reputational damage.

Recommendation

• Apply the patch or upgrade to @actual-app/sync-server version 26.4.0 or later to remediate CVE-2026-33318.
• Implement server-side checks to restrict access to the /account/change-password endpoint to password-authenticated sessions only, as recommended in the advisory.
• Require current-password confirmation before accepting a new password via the /account/change-password endpoint.
• Enforce the active status and remove client control over login method selection in the getLoginMethod() function.
• As an immediate mitigation for existing deployments, administrators who have fully migrated to OpenID and do not need password auth can remove the orphaned password row using the SQL command: DELETE FROM auth WHERE method = 'password';.