An improper certificate validation vulnerability [CWE-295] in FortiClientWindows 6.4 all versions, 7.0.0 through 7.0.7, FortiClientMac 6.4 all versions, 7.0 all versions, 7.2.0 through 7.2.4, FortiClientLinux 6.4 all versions, 7.0 all versions, 7.2.0 through 7.2.4, FortiClientAndroid 6.4 all versions, 7.0 all versions, 7.2.0 and FortiClientiOS 5.6 all versions, 6.0.0 through 6.0.1, 7.0.0 through 7.0.6 SAML SSO feature may allow an unauthenticated attacker to man-in-the-middle the communication between the FortiClient and  both the service provider and the identity provider.

FortiClient before 4.3.5.472 on Windows, before 4.0.3.134 on Mac OS X, and before 4.0 on Android; FortiClient Lite before 4.3.4.461 on Windows; FortiClient Lite 2.0 through 2.0.0223 on Android; and FortiClient SSL VPN before 4.0.2258 on Linux proceed with an SSL session after determining that the server's X.509 certificate is invalid, which allows man-in-the-middle attackers to obtain sensitive information by leveraging a password transmission that occurs before the user warning about the certificate problem.

The Internet Key Exchange version 1 (IKEv1) implementations in Fortinet FortiOS 2.50, 2.80 and 3.0, FortiClient 2.0,; and FortiManager 2.80 and 3.0 allow remote attackers to cause a denial of service (termination of a process that is automatically restarted) via IKE packets with invalid values of certain IPSec attributes, as demonstrated by the PROTOS ISAKMP Test Suite for IKEv1. NOTE: due to the lack of details in the vendor advisory, it is unclear which of CVE-2005-3666, CVE-2005-3667, and/or CVE-2005-3668 this issue applies to.