CVE-2026-20106
📋 TL;DR
An unauthenticated remote attacker can send crafted packets to Cisco ASA/FTD Remote Access SSL VPN, HTTP management, or MUS services to exhaust device memory, causing a denial of service requiring manual reboot. This affects Cisco Secure Firewall ASA Software and Secure Firewall Threat Defense (FTD) Software with vulnerable configurations.
💻 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 device unavailability requiring physical reboot, disrupting all network traffic and security functions until restored.
Likely Case
Intermittent service disruptions affecting VPN connectivity and management access until device is rebooted.
If Mitigated
Minimal impact with proper network segmentation and access controls limiting exposure to trusted sources.
🎯 Exploit Status
Exploitation requires sending crafted packets to vulnerable services. No authentication required.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Refer to Cisco advisory for fixed releases
Vendor Advisory: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-vpn-m9sx6MbC
Restart Required: Yes
Instructions:
1. Review Cisco advisory for fixed software releases. 2. Download appropriate patched version. 3. Backup configuration. 4. Apply patch following Cisco upgrade procedures. 5. Reboot device.
🔧 Temporary Workarounds
Disable vulnerable services
allDisable Remote Access SSL VPN, HTTP management, and MUS functionality if not required
no webvpn
no http server enable
no management-access
Restrict access with ACLs
allApply access control lists to limit which IPs can reach vulnerable services
access-list VPN-ACL extended permit ip trusted-net any
access-group VPN-ACL in interface outside
🧯 If You Can't Patch
- Implement strict network segmentation to isolate vulnerable devices
- Deploy intrusion prevention systems to detect and block exploitation attempts
🔍 How to Verify
Check if Vulnerable:
Check if device has Remote Access SSL VPN, HTTP management, or MUS enabled using 'show running-config | include webvpn|http server|management-access'Check Version:
show version | include SoftwareVerify Fix Applied:
Verify running software version matches patched release from Cisco advisory using 'show version'📡 Detection & Monitoring
Log Indicators:
- Memory exhaustion warnings
- Process crashes
- VPN connection failures
- Device becoming unresponsive
Network Indicators:
- Unusual traffic patterns to VPN/management ports
- Crafted packets to TCP/443, TCP/80, or management ports
SIEM Query:
source="cisco-asa" AND (event_id=722041 OR event_id=722042 OR memory_usage>90%)