LinkAce is a self-hosted archive to collect website links. Prior to 2.5.6, the setup database configuration flow on uninitialized LinkAce instances accepts attacker-controlled database credential fields and writes them back into .env without escaping. A remote attacker who can reach the setup endpoints and supply a database they control can inject mail configuration variables and achieve command execution when the application later sends mail. This vulnerability is fixed in 2.5.6.