CVE-2021-31854: McAfee Agent Privilege Escalation Flaw

CVE-2021-31854 Overview

A command injection vulnerability exists in McAfee Agent (MA) for Windows prior to version 5.7.5 that allows local users to inject arbitrary shell code into the file cleanup.exe. The malicious clean.exe file is placed into the relevant folder and executed by running the McAfee Agent deployment feature located in the System Tree. An attacker may exploit this vulnerability to obtain a reverse shell which can lead to privilege escalation to obtain root privileges.

Critical Impact

This command injection vulnerability allows attackers to achieve privilege escalation through arbitrary shell code execution, potentially gaining root-level access to affected Windows systems running vulnerable versions of McAfee Agent.

Affected Products

• McAfee Agent for Windows prior to version 5.7.5
• Systems utilizing McAfee Agent deployment features via System Tree
• Enterprise environments with McAfee endpoint management infrastructure

Discovery Timeline

• 2022-01-19 - CVE-2021-31854 published to NVD
• 2026-02-24 - Last updated in NVD database

Technical Details for CVE-2021-31854

Vulnerability Analysis

This vulnerability is classified as CWE-78 (Improper Neutralization of Special Elements used in an OS Command), commonly referred to as OS Command Injection. The flaw resides in how McAfee Agent handles the cleanup.exe process during deployment operations. The application fails to properly validate or sanitize input before incorporating it into system commands, allowing attackers to inject malicious shell code.

The attack requires local access to the system with the ability to place a malicious executable file in a location where the McAfee Agent deployment process will execute it. Once the deployment feature is triggered through the System Tree management interface, the injected code executes with elevated privileges, enabling the attacker to establish a reverse shell connection.

Root Cause

The root cause of CVE-2021-31854 stems from inadequate input validation and sanitization mechanisms within the McAfee Agent's deployment workflow. The cleanup.exe executable processing routine does not properly verify the integrity or authenticity of files it interacts with, nor does it sanitize command parameters before execution. This allows specially crafted malicious files to be executed within the trusted context of the McAfee Agent process.

Attack Vector

The attack vector for this vulnerability is local, requiring an attacker to have existing access to the target Windows system. The exploitation process involves:

1. Crafting a malicious executable file containing arbitrary shell code
2. Placing the malicious clean.exe file into the directory where McAfee Agent expects deployment-related executables
3. Triggering the McAfee Agent deployment feature through the System Tree interface
4. The malicious code executes with elevated privileges, potentially establishing a reverse shell
5. Leveraging the reverse shell access to escalate privileges to root level

The vulnerability does not require authentication but does require user interaction to trigger the deployment feature, though this interaction may occur during routine administrative operations.

Detection Methods for CVE-2021-31854

Indicators of Compromise

• Unexpected or modified clean.exe or cleanup.exe files in McAfee Agent installation directories
• Suspicious outbound network connections from McAfee Agent processes indicating potential reverse shell activity
• Unusual process creation events where McAfee Agent spawns unexpected child processes
• File integrity monitoring alerts for McAfee Agent deployment directories

Detection Strategies

• Implement file integrity monitoring on McAfee Agent installation directories to detect unauthorized file modifications
• Monitor process execution chains for anomalous behavior involving McAfee Agent components
• Configure endpoint detection rules to identify command injection patterns in McAfee Agent processes
• Deploy network monitoring to detect reverse shell connections originating from McAfee Agent executables

Monitoring Recommendations

• Enable detailed logging for McAfee Agent deployment operations and System Tree activities
• Implement application whitelisting to prevent execution of unauthorized executables in McAfee Agent directories
• Configure SIEM rules to correlate McAfee Agent process activity with suspicious network connections
• Establish baseline behavior for McAfee Agent processes to identify deviations indicative of exploitation

How to Mitigate CVE-2021-31854

Immediate Actions Required

• Upgrade McAfee Agent for Windows to version 5.7.5 or later immediately
• Audit McAfee Agent installation directories for any unauthorized or modified executable files
• Restrict local access permissions to McAfee Agent installation and deployment directories
• Review and limit user access to System Tree deployment features to authorized administrators only

Patch Information

McAfee has released a security update addressing this vulnerability. Organizations should upgrade to McAfee Agent version 5.7.5 or later to remediate CVE-2021-31854. Detailed information about the security fix is available in the McAfee Security Advisory. Prior to patching, verify the integrity of existing McAfee Agent installations and perform a full scan for potential indicators of compromise.

Workarounds

• Implement strict access controls on McAfee Agent deployment directories using Windows NTFS permissions
• Enable application control policies to prevent unauthorized executable modifications in McAfee Agent folders
• Temporarily disable or restrict access to the System Tree deployment feature until patching is completed
• Deploy endpoint detection and response (EDR) solutions to monitor for exploitation attempts in real-time