Apple has just released an update to bring AirPort Express and Extreme, and Time Capsule Base Stations, with 802.11n to firmware version 7.8.1. Base Stations with 802.11ac were updated on 31 May; this update addresses a similar if not identical list of security bugs in those with 802.11n. Those vulnerabilities include remote attacks.

If your Base Station is included, you should perform this update as soon as possible, using AirPort Utility.