CVE-2026-20064
📋 TL;DR
A local authenticated attacker with low privileges can cause Cisco Secure Firewall Threat Defense devices to unexpectedly reload by sending crafted CLI commands, resulting in denial of service. This affects organizations using vulnerable FTD software versions.
💻 Affected Systems
- 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
Persistent DoS attacks could render firewall unavailable for extended periods, disrupting network security and connectivity.
Likely Case
Temporary service disruption during device reload, causing brief network outages until system restarts.
If Mitigated
Minimal impact with proper access controls limiting low-privileged CLI access and monitoring for suspicious commands.
🎯 Exploit Status
Exploitation requires authenticated CLI access; no public exploit code mentioned in advisory.
🛠️ 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-ftd-cmd-inj-mTzGZexf
Restart Required: Yes
Instructions:
1. Review Cisco advisory for affected versions. 2. Download appropriate fixed software version from Cisco. 3. Schedule maintenance window. 4. Backup configuration. 5. Apply update following Cisco FTD upgrade procedures. 6. Verify system functionality post-update.
🔧 Temporary Workarounds
Restrict CLI Access
allLimit CLI access to trusted administrators only; remove or restrict low-privileged CLI accounts
configure terminal
username [username] privilege 15
end
write memory
Command Authorization
allImplement command authorization to restrict available commands for low-privileged users
aaa authorization exec default local
privilege exec level 15 configure terminal
🧯 If You Can't Patch
- Implement strict access controls: Only allow CLI access to necessary administrative personnel with highest privilege levels
- Monitor CLI logs for unusual command patterns and implement alerting for unexpected reload commands
🔍 How to Verify
Check if Vulnerable:
Check current FTD software version and compare against affected versions in Cisco advisoryCheck Version:
show version | include VersionVerify Fix Applied:
Verify installed version matches or exceeds fixed version listed in Cisco advisory📡 Detection & Monitoring
Log Indicators:
- Unexpected system reloads
- CLI commands from low-privileged users causing errors
- Authentication logs showing CLI access from unauthorized accounts
Network Indicators:
- Firewall becoming unresponsive
- Loss of network connectivity through firewall
- Increased latency during reload events
SIEM Query:
source="cisco_ftd" AND (event_type="system_reload" OR command="reload" OR message="%SYS-5-RESTART")