OpenStack Identity (Keystone) Folsom 2012.2.4 and earlier, Grizzly before 2013.1.1, and Havana does not immediately revoke the authentication token when deleting a user through the Keystone v2 API, which allows remote authenticated users to retain access via the token.
CWE-287 - Improper Authentication
Improper (or broken) authentication attacks are widespread, and have accounted for many of the worst data breaches in recent years. Improper authentication attacks are a class of vulnerabilities where an attacker impersonates a legitimate user by exploiting weaknesses in either session management or credential management to gain access to the user’s account. This can result in disclosure of sensitive information, and can lead to system compromise, theft, identity theft, and fraud.