Race condition in the Phone Proxy component in Cisco Adaptive Security Appliance (ASA) Software 9.1(.3) and earlier allows remote attackers to bypass sec_db authentication and provide certain pass-through services to untrusted devices via a crafted configuration-file TFTP request, aka Bug ID CSCuj66766.
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.