The SSL-VPN feature in Fortinet FortiOS before 4.3.13 only checks the first byte of the TLS MAC in finished messages, which makes it easier for remote attackers to spoof encrypted content via a crafted MAC field.
Improper Input Validation The product receives input or data, but it does
not validate or incorrectly validates that the input has the
properties that are required to process the data safely and
correctly.