An Insufficient Session Expiration vulnerability [CWE-613] in FortiOS SSL-VPN version 7.6.0, version 7.4.6 and below, version 7.2.10 and below, 7.0 all versions, 6.4 all versions may allow an attacker in possession of a cookie used to log in the SSL-VPN portal to log in again, although the session has expired or was logged out.
According to WASC, “Insufficient Session Expiration is when a web site permits an attacker to reuse old session credentials or session IDs for authorization.”