CVE-2021-26737 : Vulnerability Insights and Analysis

This article provides an in-depth overview of CVE-2021-26737 focusing on the Zscaler Client Connector vulnerability in macOS and its potential impacts, technical details, and mitigation strategies.

Understanding CVE-2021-26737

CVE-2021-26737 highlights a security vulnerability in the Zscaler Client Connector for macOS, affecting versions prior to 3.6. The flaw could allow a local attacker to shut down the Zscaler tunnel by exploiting a race condition.

What is CVE-2021-26737?

The Zscaler Client Connector for macOS versions before 3.6 lacked proper validation of RPC clients, enabling a local adversary with insufficient privileges to exploit a race condition and disrupt the Zscaler tunnel.

The Impact of CVE-2021-26737

The vulnerability (CAPEC-26) poses a medium-severity risk with a CVSS v3.1 base score of 5.5. While requiring low attack complexity and privileges, it can lead to a high impact on availability without compromising confidentiality or integrity.

Technical Details of CVE-2021-26737

The technical details of CVE-2021-26737 include:

Vulnerability Description

The Zscaler Client Connector for macOS failed to adequately validate RPC clients, resulting in a security loophole that could be exploited through a race condition.

Affected Systems and Versions

The vulnerability affects versions of the Zscaler Client Connector for macOS that are earlier than 3.6.

Exploitation Mechanism

A local attacker, even with low privileges, could leverage the race condition within the RPC validation process to disrupt the Zscaler tunnel.

Mitigation and Prevention

To mitigate the risks associated with CVE-2021-26737, the following steps are recommended:

Immediate Steps to Take

Upgrade Zscaler Client Connector for macOS to version 3.6 or higher.
Monitor system logs and anomalistic behavior for signs of exploitation.

Long-Term Security Practices

Regularly update software and apply security patches promptly.
Implement strong access controls and privilege management policies.

Patching and Updates

Zscaler has released a patch addressing the vulnerability in version 3.6. Ensure timely installation of updates and follow best security practices to prevent potential exploitation.