Vulnerability Note VU#319904
Pulse Secure Linux client GUI fails to validate SSL certificates
Original Release date: 01 Feb 2018 | Last revised: 01 Feb 2018

Overview
The Pulse Secure Linux client GUI fails to validate SSL certificates, which can allow an attacker to modify connection settings.

Description
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.

Impact
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.

Solution
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.

Vendor Information (Learn More)

VendorStatusDate NotifiedDate UpdatedPulse SecureAffected11 Dec 201701 Feb 2018If you are a vendor and your product is affected, let
us know.

CVSS Metrics (Learn More)

Group
Score
Vector

Base
5.1
AV:N/AC:H/Au:N/C:P/I:P/A:P

Temporal
4.0
E:POC/RL:OF/RC:C

Environmental
3.0
CDP:ND/TD:M/CR:ND/IR:ND/AR:ND

References

http://kb.pulsesecure.net/articles/Pulse_Security_Advisories/SA43620

Credit

This vulnerability was reported by Will Dormann of the CERT/CC.
This document was written by Will Dormann.

Other Information

CVE IDs:
CVE-2018-6374

Date Public:
01 Feb 2018

Date First Published:
01 Feb 2018

Date Last Updated:
01 Feb 2018

Document Revision:
6

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