Fortinet Antivirus (AV) Engine

An insufficient verification of data authenticity vulnerability [CWE-345] in FortiClient, FortiMail and FortiOS AV engines version 6.2.168 and below and version 6.4.274 and below may allow an attacker to bypass the AV engine via manipulating MIME attachment with junk and pad characters in base64.

FortiOS 6.2 running AV engine version 6.00142 and below, FortiOS 6.4 running AV engine version 6.00144 and below and FortiClient 6.2 running AV engine version 6.00137 and below may not immediately detect certain types of malformed or non-standard RAR archives, potentially containing malicious files. Based on the samples provided, FortiClient will detect the malicious files upon trying extraction by real-time scanning and FortiGate will detect the malicious archive if Virus Outbreak Prevention is enabled.