CVE-2024-20338: Cisco Secure Client Privilege Escalation

CVE-2024-20338 Overview

A privilege escalation vulnerability exists in the ISE Posture (System Scan) module of Cisco Secure Client for Linux. This vulnerability allows an authenticated, local attacker to elevate privileges on an affected device by exploiting an uncontrolled search path element (CWE-427). An attacker could exploit this vulnerability by copying a malicious library file to a specific directory in the filesystem and persuading an administrator to restart a specific process, ultimately achieving arbitrary code execution with root privileges.

Critical Impact

Successful exploitation allows local attackers to execute arbitrary code with root privileges on affected Linux systems running Cisco Secure Client.

Affected Products

• Cisco Secure Client for Linux
• Linux Kernel (as underlying operating system)
• Systems utilizing the ISE Posture (System Scan) module

Discovery Timeline

• 2024-03-06 - CVE-2024-20338 published to NVD
• 2025-07-22 - Last updated in NVD database

Technical Details for CVE-2024-20338

Vulnerability Analysis

This vulnerability stems from improper handling of library search paths within the ISE Posture module of Cisco Secure Client for Linux. The application fails to properly validate or restrict the directories from which shared libraries are loaded, creating an uncontrolled search path condition. When the application searches for required libraries during execution, it may inadvertently load attacker-controlled malicious libraries if they are placed in directories that appear earlier in the search path.

The vulnerability requires local access and authentication, meaning an attacker must already have a foothold on the target system. However, the impact is significant because successful exploitation results in complete privilege escalation to root, allowing full system compromise.

Root Cause

The root cause is an uncontrolled search path element (CWE-427) in the ISE Posture module. The application does not properly restrict or validate the directories included in the library search path, allowing an attacker to inject malicious shared library files into locations that the application trusts. When an administrator restarts the affected process, the malicious library is loaded with elevated privileges.

Attack Vector

The attack requires local access and follows these steps:

1. An authenticated attacker identifies the library search path used by the ISE Posture module
2. The attacker crafts a malicious shared library with the same name as a library loaded by the application
3. The attacker places this malicious library in a directory that appears in the uncontrolled search path
4. The attacker persuades an administrator to restart the specific process (requiring user interaction)
5. Upon restart, the application loads the malicious library with root privileges, executing the attacker's code

The attack requires user interaction from an administrator to trigger the vulnerable code path by restarting the affected process. This constraint limits the exploitability but does not eliminate the significant risk posed by successful exploitation.

Detection Methods for CVE-2024-20338

Indicators of Compromise

• Unexpected shared library files appearing in system directories or Cisco Secure Client installation paths
• Unusual library files with recent modification timestamps in directories within the library search path
• Process execution anomalies or unexpected child processes spawned by Cisco Secure Client components
• Unauthorized privilege escalation events logged in system audit logs

Detection Strategies

• Monitor file system changes to directories within the Cisco Secure Client installation path and common library directories
• Implement file integrity monitoring (FIM) on critical directories associated with the ISE Posture module
• Review system logs for unexpected process restarts of Cisco Secure Client services
• Enable detailed auditing of library loading operations on Linux systems using LD_DEBUG or similar mechanisms

Monitoring Recommendations

• Configure SentinelOne to monitor for suspicious library loading patterns and privilege escalation attempts
• Implement endpoint detection rules to alert on new shared library files in monitored directories
• Enable process monitoring to detect anomalous behavior following Cisco Secure Client service restarts
• Review administrative access logs to identify potential social engineering attempts targeting administrators

How to Mitigate CVE-2024-20338

Immediate Actions Required

• Review the Cisco Security Advisory for patch availability and update instructions
• Upgrade Cisco Secure Client for Linux to a patched version as specified in the advisory
• Audit systems running Cisco Secure Client for any unauthorized library files in relevant directories
• Restrict write access to directories in the library search path to prevent unauthorized modifications

Patch Information

Cisco has released a security advisory addressing this vulnerability. Administrators should consult the official Cisco Security Advisory (cisco-sa-secure-privesc-sYxQO6ds) for specific version information and upgrade guidance. Apply the recommended patches as soon as possible to remediate this vulnerability.

Workarounds

• Restrict file system permissions on directories within the Cisco Secure Client library search path to prevent unauthorized writes
• Implement strict access controls limiting which users can modify files in system library directories
• Use application whitelisting or integrity verification to detect unauthorized library modifications
• Educate administrators about the risk of restarting services on potentially compromised systems

# Example: Restrict permissions on library directories
# Identify directories used by Cisco Secure Client
ls -la /opt/cisco/secureclient/

# Ensure proper ownership and permissions
sudo chown -R root:root /opt/cisco/secureclient/
sudo chmod -R 755 /opt/cisco/secureclient/
sudo chmod -R go-w /opt/cisco/secureclient/

# Enable file integrity monitoring
sudo aide --init
sudo cp /var/lib/aide/aide.db.new /var/lib/aide/aide.db