FortiMail - Salted Digest vulnerable to length extension attacks
A missing cryptographic step in the implementation of the hash digest algorithm in FortiMail may allow an unauthenticated attacker to tamper with signed URLs by appending further data which allows bypass of signature verification.
FortiMail 6.4.4 and below,
FortiMail 6.2.6 and below.
Upgrade to FortiMail version 7.0.0.
Upgrade to FortiMail version 6.4.5.