The (1) mdare64_48.sys, (2) mdare32_48.sys, (3) mdare32_52.sys, (4) mdare64_52.sys, and (5) Fortishield.sys drivers in Fortinet FortiClient before 5.2.4 do not properly restrict access to the API for management of processes and the Windows registry, which allows local users to obtain a privileged handle to a PID and possibly have unspecified other impact, as demonstrated by a 0x2220c8 ioctl call.

The Endpoint Control protocol implementation in Fortinet FortiClient 5.2.3.091 for Android and 5.2.028 for iOS does not validate certificates, which makes it easier for man-in-the-middle attackers to spoof servers via a crafted certificate.

Fortinet FortiClient 5.2.028 for iOS does not validate certificates, which makes it easier for man-in-the-middle attackers to spoof SSL VPN servers via a crafted certificate.

The qm class in Fortinet FortiClient 5.2.3.091 for Android uses a hardcoded encryption key of FoRtInEt!AnDrOiD, which makes it easier for attackers to obtain passwords and possibly other sensitive data by leveraging the key to decrypt data in the Shared Preferences.

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.

Format string vulnerability in Fortinet FortiClient 3.0.614, and possibly earlier, allows local users to execute arbitrary code via format string specifiers in the VPN connection name.

The fortimon.sys device driver in Fortinet FortiClient Host Security 3.0 MR5 Patch 3 and earlier does not properly initialize its DeviceExtension, which allows local users to access kernel memory and execute arbitrary code via a crafted request.