A password protected door leads to a secret stash. Passcode is "0340"

Anna and Langley's hidden stash in Sevastopol in Alien: Isolation.

Located near the Departures terminal

The most notable loot you can find here is a Medikit Blueprint

Puzzle solution

The passcode for this gate can be found in an email titled "Moved Our Stash" that can be accessed through one of the SEVASTOLINK Terminals

The passcode is: "0340"