CVE-2021-26738
📋 TL;DR
This vulnerability in Zscaler Client Connector for macOS allows local attackers to execute arbitrary code with root privileges by exploiting an unquoted search path in the PATH variable. It affects macOS systems running Zscaler Client Connector versions prior to 3.7. Attackers need local access to the system to exploit this privilege escalation vulnerability.
💻 Affected Systems
- Zscaler Client Connector
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Local attacker gains full root privileges on the macOS system, enabling complete system compromise, data theft, persistence installation, and lateral movement.
Likely Case
Privilege escalation from standard user to root, allowing installation of malware, credential harvesting, and bypassing security controls.
If Mitigated
Attack limited to standard user privileges if proper access controls prevent local code execution or if PATH manipulation is restricted.
🎯 Exploit Status
Exploitation requires local access to the system. Unquoted search path vulnerabilities are well-understood attack vectors with established exploitation patterns.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 3.7 and later
Restart Required: Yes
Instructions:
1. Download Zscaler Client Connector version 3.7 or later from official Zscaler sources. 2. Install the update following standard macOS software installation procedures. 3. Restart the system to ensure all components are updated.
🔧 Temporary Workarounds
Restrict local user privileges
macOSLimit standard user accounts' ability to modify PATH environment variables or execute arbitrary binaries.
Monitor for suspicious PATH modifications
macOSImplement monitoring for unauthorized changes to PATH environment variables or execution of unexpected binaries.
🧯 If You Can't Patch
- Implement strict access controls to prevent unauthorized local access to affected systems
- Deploy application whitelisting to prevent execution of unauthorized binaries
🔍 How to Verify
Check if Vulnerable:
Check Zscaler Client Connector version in macOS System Preferences > Zscaler Client Connector > About. If version is below 3.7, system is vulnerable.Check Version:
defaults read /Applications/Zscaler/Zscaler.app/Contents/Info.plist CFBundleShortVersionStringVerify Fix Applied:
Verify Zscaler Client Connector version is 3.7 or higher in System Preferences > Zscaler Client Connector > About.📡 Detection & Monitoring
Log Indicators:
- Unexpected privilege escalation events
- Execution of binaries from unusual PATH locations
- Modifications to PATH environment variables
Network Indicators:
- None - this is a local privilege escalation vulnerability
SIEM Query:
source="macos" AND (event_type="privilege_escalation" OR process_name="Zscaler" AND action="execute")🔗 References
- https://help.zscaler.com/client-connector/client-connector-app-release-summary-2022?applicable_category=macOS&applicable_version=3.7&deployment_date=2022-08-19&id=1414851
- https://help.zscaler.com/client-connector/client-connector-app-release-summary-2022?applicable_category=macOS&applicable_version=3.7&deployment_date=2022-08-19&id=1414851
