CVE-2025-20206
📋 TL;DR
This vulnerability allows authenticated local attackers on Windows systems with Cisco Secure Client and Secure Firewall Posture Engine installed to perform DLL hijacking attacks via crafted IPC messages. Successful exploitation could lead to arbitrary code execution with SYSTEM privileges. Only Windows systems with both Cisco Secure Client and the Posture Engine component are affected.
💻 Affected Systems
- Cisco Secure Client for Windows with Secure Firewall Posture Engine (formerly HostScan)
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Attacker gains SYSTEM privileges and full control of the affected Windows machine, potentially leading to complete system compromise, data theft, and lateral movement within the network.
Likely Case
Privilege escalation from standard user to SYSTEM, enabling installation of persistent malware, credential harvesting, and bypassing security controls.
If Mitigated
Limited impact due to proper access controls, monitoring, and network segmentation preventing lateral movement even if local privilege escalation occurs.
🎯 Exploit Status
Requires authenticated local access, knowledge of IPC messaging, and ability to place malicious DLLs in specific locations. The attacker needs valid Windows user credentials.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Update to latest Cisco Secure Client version as specified in the advisory
Vendor Advisory: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-secure-dll-injection-AOyzEqSg
Restart Required: No
Instructions:
1. Download the latest Cisco Secure Client from Cisco's official site. 2. Install the update on all affected Windows systems. 3. Verify the installation completed successfully.
🔧 Temporary Workarounds
Remove Posture Engine Component
WindowsUninstall the Secure Firewall Posture Engine component if not required for your deployment
Control Panel > Programs > Uninstall a program > Select 'Cisco Secure Firewall Posture Engine' > Uninstall
Restrict DLL Loading Locations
WindowsImplement application control policies to prevent DLL loading from untrusted directories
🧯 If You Can't Patch
- Implement strict least privilege access controls to limit who has local authenticated access to vulnerable systems
- Enable Windows Defender Application Control or similar solutions to block unauthorized DLL loading
🔍 How to Verify
Check if Vulnerable:
Check if Cisco Secure Client with Posture Engine is installed: Look for 'Cisco Secure Client' and 'Cisco Secure Firewall Posture Engine' in installed programs listCheck Version:
Open Cisco Secure Client GUI and check version in About section, or check registry at HKEY_LOCAL_MACHINE\SOFTWARE\Cisco\Cisco AnyConnect Secure Mobility ClientVerify Fix Applied:
Verify Cisco Secure Client version is updated to the patched version specified in the advisory📡 Detection & Monitoring
Log Indicators:
- Unusual process creation from Cisco Secure Client processes
- DLL loading from non-standard locations by ciscod.exe or related processes
- Failed DLL loading attempts in application logs
Network Indicators:
- Unusual IPC communication patterns on local system
- Outbound connections from Cisco Secure Client processes to unexpected destinations
SIEM Query:
Process Creation where (Parent Process Name contains 'ciscod' OR Parent Process Name contains 'vpnagent') AND (Command Line contains 'dll' OR Image Loaded contains suspicious path)