CVE-2025-20244
📋 TL;DR
This vulnerability allows authenticated VPN users to send specially crafted HTTP requests to Cisco ASA/FTD Remote Access SSL VPN services, causing the device to reload and creating a denial of service condition. It affects organizations using Cisco Secure Firewall ASA Software and Cisco Secure Firewall Threat Defense Software with Remote Access SSL VPN enabled.
💻 Affected Systems
- Cisco Secure Firewall Adaptive Security Appliance (ASA) Software
- Cisco Secure Firewall Threat Defense (FTD) Software
⚠️ Manual Verification Required
This CVE does not have specific version information in our database, so automatic vulnerability detection cannot determine if your system is affected.
Why? The CVE database entry doesn't specify which versions are vulnerable (no version ranges provided by the vendor/NVD).
🔒 Custom verification scripts are available for registered users. Sign up free to download automated test scripts.
- Review the CVE details at NVD
- Check vendor security advisories for your specific version
- Test if the vulnerability is exploitable in your environment
- Consider updating to the latest version as a precaution
⚠️ Risk & Real-World Impact
Worst Case
Complete VPN service disruption affecting all remote users, requiring device reboot and potential service restoration delays.
Likely Case
Temporary VPN service outage affecting remote workforce connectivity until device automatically reloads.
If Mitigated
Minimal impact with proper network segmentation and monitoring allowing quick detection and response.
🎯 Exploit Status
Requires VPN user authentication but exploitation is straightforward once authenticated
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check Cisco advisory for specific fixed versions
Vendor Advisory: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-vpnwebs-dos-hjBhmBsX
Restart Required: Yes
Instructions:
1. Review Cisco advisory for affected versions 2. Download appropriate fixed software 3. Schedule maintenance window 4. Apply update following Cisco upgrade procedures 5. Verify service restoration
🔧 Temporary Workarounds
Disable Remote Access SSL VPN
allTemporarily disable the vulnerable service if not critically needed
no webvpn
no enable outside
Restrict VPN Access
allLimit VPN access to trusted users only using access control lists
access-list VPN-ACL permit ip host [trusted-ip] any
access-group VPN-ACL in interface outside
🧯 If You Can't Patch
- Implement strict VPN user authentication and monitoring
- Deploy network segmentation to isolate VPN traffic and limit blast radius
🔍 How to Verify
Check if Vulnerable:
Check device version against Cisco advisory and verify Remote Access SSL VPN is enabledCheck Version:
show version | include VersionVerify Fix Applied:
Verify installed version matches fixed version in Cisco advisory and test VPN connectivity📡 Detection & Monitoring
Log Indicators:
- Unexpected device reloads
- VPN service crashes
- HTTP parsing errors in VPN logs
Network Indicators:
- Sudden VPN service unavailability
- Multiple HTTP requests from single VPN user
SIEM Query:
source="cisco-asa" AND (event_id=713172 OR message="%ASA-6-713172") OR (message="reload" AND source_ip IN vpn_users)