CVE-2024-20391: Cisco Secure Client Privilege Escalation

CVE-2024-20391 Overview

A privilege escalation vulnerability exists in the Network Access Manager (NAM) module of Cisco Secure Client that could allow an unauthenticated attacker with physical access to an affected device to elevate privileges to SYSTEM level. This vulnerability stems from missing authentication on a specific function within the NAM module, enabling arbitrary code execution with the highest system privileges on Windows devices.

Critical Impact

An attacker with physical access can achieve SYSTEM-level privileges on affected Windows systems, potentially leading to complete system compromise, data exfiltration, and lateral movement within enterprise networks.

Affected Products

• Cisco Secure Client (with Network Access Manager module enabled)
• Microsoft Windows (as the underlying operating system)
• Enterprise deployments utilizing NAM for network access control

Discovery Timeline

• 2024-05-15 - CVE-2024-20391 published to NVD
• 2025-07-22 - Last updated in NVD database

Technical Details for CVE-2024-20391

Vulnerability Analysis

This vulnerability is classified under CWE-306 (Missing Authentication for Critical Function), which represents a significant security flaw in access control implementation. The Network Access Manager module, which handles network authentication and connection management for Cisco Secure Client, exposes a function that lacks proper authentication validation.

The physical attack vector requirement limits remote exploitation, but in scenarios involving shared workstations, kiosk deployments, or insider threats, this vulnerability presents a substantial risk. Once exploited, the attacker gains SYSTEM privileges—the highest privilege level on Windows systems—allowing complete control over the affected device.

Root Cause

The root cause of CVE-2024-20391 is the absence of authentication controls on a critical function within the NAM module. When the NAM component processes certain requests, it fails to verify whether the requesting entity has appropriate authorization to invoke privileged operations. This authentication gap allows local attackers with physical access to bypass security controls and execute code in a highly privileged context.

Attack Vector

The attack requires physical access to a Windows device running Cisco Secure Client with the NAM module installed and active. An attacker with console access can interact with the vulnerable NAM component to trigger the unauthenticated function, escalating privileges from any local context to SYSTEM level.

The exploitation pathway involves:

1. Gaining physical access to a target Windows endpoint running Cisco Secure Client
2. Interacting with the NAM module through its exposed interfaces
3. Invoking the unauthenticated function to execute arbitrary code
4. Achieving SYSTEM-level privileges for further malicious activities

Due to the sensitive nature of this vulnerability, specific exploitation details are not publicly documented. Refer to the Cisco Security Advisory for technical guidance.

Detection Methods for CVE-2024-20391

Indicators of Compromise

• Unexpected processes spawned with SYSTEM privileges associated with Cisco Secure Client components
• Anomalous authentication events or privilege escalation attempts in Windows Security logs
• Unusual NAM module activity or configuration changes
• Creation of unauthorized user accounts or scheduled tasks with elevated privileges

Detection Strategies

• Monitor Windows Event Logs for privilege escalation events (Event ID 4672, 4624) involving Cisco Secure Client processes
• Implement endpoint detection rules to identify unauthorized SYSTEM-level process creation
• Deploy SentinelOne Singularity Platform to detect behavioral anomalies associated with privilege escalation
• Configure alerts for unexpected modifications to NAM module configurations or related registry keys

Monitoring Recommendations

• Enable detailed process auditing on endpoints running Cisco Secure Client
• Establish baselines for normal NAM module behavior to identify deviations
• Implement physical security controls and access logging for sensitive workstations
• Regularly review endpoint telemetry for signs of local privilege escalation attempts

How to Mitigate CVE-2024-20391

Immediate Actions Required

• Apply the security patch provided by Cisco as referenced in the official advisory
• Restrict physical access to systems running Cisco Secure Client with NAM enabled
• Implement additional endpoint monitoring on high-value assets
• Review and audit user accounts for any unauthorized privilege changes

Patch Information

Cisco has released a security update addressing this vulnerability. Organizations should consult the Cisco Security Advisory (cisco-sa-secure-nam-priv-esc-szu2vYpZ) for specific version information and download links. Prioritize patching systems that are physically accessible to untrusted users or located in shared environments.

Workarounds

• Disable the NAM module if not required for network access management functions
• Implement strict physical access controls to limit console access to trusted personnel only
• Enable BitLocker or full-disk encryption to prevent offline attacks
• Deploy application whitelisting to prevent unauthorized code execution

# Verify Cisco Secure Client version on Windows systems
# Run in elevated PowerShell to check installed version
Get-WmiObject -Class Win32_Product | Where-Object {$_.Name -like "*Cisco Secure Client*"} | Select-Object Name, Version

# Check if NAM module is installed and enabled
Get-Service -Name "acnamwire" -ErrorAction SilentlyContinue | Select-Object Name, Status, StartType