CVE-2023-20178
📋 TL;DR
This vulnerability allows a low-privileged local attacker on Windows systems with Cisco AnyConnect or Secure Client to elevate privileges to SYSTEM level by exploiting improper permissions in the temporary directory created during the client update process. The attack requires the user to have already established a VPN connection and have local authenticated access.
💻 Affected Systems
- Cisco AnyConnect Secure Mobility Client for Windows
- Cisco Secure Client for Windows
📦 What is this software?
Anyconnect Secure Mobility Client by Cisco
⚠️ Risk & Real-World Impact
Worst Case
Attacker gains full SYSTEM privileges on the Windows host, enabling complete system compromise, persistence installation, credential theft, and lateral movement across the network.
Likely Case
Privilege escalation from standard user to SYSTEM, allowing installation of malware, disabling security controls, and accessing sensitive system resources.
If Mitigated
Limited to local authenticated users only; network segmentation and proper endpoint controls reduce lateral movement potential.
🎯 Exploit Status
Exploitation requires local authenticated access and abuse of Windows installer process functions.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 4.10.07061 and later
Vendor Advisory: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ac-csc-privesc-wx4U4Kw
Restart Required: Yes
Instructions:
1. Download latest version from Cisco Software Center. 2. Uninstall current version. 3. Install patched version. 4. Restart system.
🔧 Temporary Workarounds
Disable automatic updates
windowsPrevent the vulnerable update process from executing automatically
Navigate to AnyConnect settings and disable 'Enable automatic updates'
Restrict local user permissions
windowsLimit which users can establish VPN connections and have local login rights
🧯 If You Can't Patch
- Restrict VPN access to only necessary users with minimal local privileges
- Implement application whitelisting to prevent unauthorized process execution
🔍 How to Verify
Check if Vulnerable:
Check Cisco AnyConnect/Secure Client version via GUI or command line: 'anyconnect.exe --version'Check Version:
anyconnect.exe --versionVerify Fix Applied:
Verify version is 4.10.07061 or higher using same method📡 Detection & Monitoring
Log Indicators:
- Unusual process creation with SYSTEM privileges from AnyConnect processes
- Failed update attempts in AnyConnect logs
Network Indicators:
- Unusual outbound connections from VPN client post-update
SIEM Query:
Process creation where parent_process contains 'anyconnect' and integrity_level='SYSTEM'