Pulse Secure is an SSL VPN solution. The Linux Pulse Secure client GUI is implemented using WebKit, and the actions taken using the GUI are implemented by overriding JavaScript functions. The WebKit component of the Linux Pulse Secure client GUI is configured to ignore SSL validation errors. This means that when the Pulse Secure Linux client GUI is used to connect to a VPN server on an untrusted network, an attacker may be able to take actions that occur as the result of a user interacting with the Pulse Secure GUI. For example, an attacker may be able to modify or create new VPN connections in the Pulse Secure GUI. An attacker can also modify the welcome message that the Pulse Secure client GUI displays to the user when a VPN connection is established as well.

By modifying traffic between a Pulse Secure Linux client GUI and a server, an attacker may be able to take actions in the Pulse Secure client GUI, as well as modify information presented to the user. This may result in the user connecting to a malicious VPN server.

Apply an update

This issue is addressed in Pulse Secure versions PULSE5.3R4.2 Software (Build 639) and PULSE5.2R9.2 Software (Build 638). Please see Pulse Secure advisory SA43620 - 2018-01 for more details. If you are unable to apply an update, please consider the following workaround:

Use the Pulse Secure Linux client CLI

By avoiding the use of the Pulse Secure Linux client GUI, the vulnerable code that does not validate certificates can be avoided.

Do not use the Pulse Secure Linux client GUI on untrusted networks

By not using the Pulse Secure Linux client GUI on an untrusted network, the risk of exploitation of this vulnerability can be minimized.