FortiMail - Improper cryptographic operations in cookie encryption potentially prone to forgery

Summary

The combination of various cryptographic issues in the session management of FortiMail, including the encryption construction of the session cookie, may allow a remote attacker already in possession of a cookie to possibly reveal and alter or forge its content, thereby escalating privileges.

Affected Products

FortiMail 6.4.4 and below.
FortiMail 6.2.6 and below.

Solutions

Upgrade to FortiMail 7.0.0.
Upgrade to FortiMail 6.4.5.

Acknowledgement

Internally discovered and reported by Giuseppe Cocomazzi of the Fortinet PSIRT Team.