On Arris Touchstone Telephony Gateway TG1682G 9.1.103J6 devices, a logout action does not immediately destroy all state on the device related to the validity of the "credential" cookie, which might make it easier for attackers to obtain access at a later time (e.g., "at least for a few minutes"). NOTE: there is no documentation stating that the web UI's logout feature was supposed to do anything beyond removing the cookie from one instance of a web browser; a client-side logout action is often not intended to address cases where a person has made a copy of a cookie outside of a browser.
According to WASC, "Insufficient Session Expiration is when a web site permits an attacker to reuse old session credentials or session IDs for authorization."