CVE-2025-20217
📋 TL;DR
An unauthenticated remote attacker can send crafted traffic through Cisco Secure Firewall Threat Defense devices to trigger an infinite loop in the Snort 3 detection engine, causing denial of service. The Snort process automatically restarts via watchdog, but repeated exploitation could maintain disruption. This affects organizations using vulnerable Cisco 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
Sustained DoS condition preventing all traffic inspection and firewall functionality, requiring manual intervention if watchdog fails or exploitation is continuous.
Likely Case
Intermittent service disruption with Snort process restarts causing packet drops and inspection gaps during restart periods.
If Mitigated
Brief service interruption during Snort restart with minimal traffic impact if network has redundancy and monitoring.
🎯 Exploit Status
Exploitation requires sending traffic through the device; simple network access suffices.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Version 7.6.0 and later
Vendor Advisory: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ftd-dos-SvKhtjgt
Restart Required: Yes
Instructions:
1. Download FTD software version 7.6.0 or later from Cisco. 2. Upload to device via FMC or CLI. 3. Deploy upgrade package. 4. Reboot device after upgrade completes.
🔧 Temporary Workarounds
Disable Snort 3 Inspection
allSwitch to Snort 2 detection engine if available, though this reduces newer threat detection capabilities.
configure via Cisco Firepower Management Center (FMC) GUI: Policies > Access Control > Advanced > Inspection Mode > Set to Snort 2
🧯 If You Can't Patch
- Implement network segmentation to limit traffic to trusted sources only.
- Deploy intrusion prevention systems (IPS) upstream to detect and block crafted traffic patterns.
🔍 How to Verify
Check if Vulnerable:
Check FTD software version via CLI: 'show version' and verify if below 7.6.0.Check Version:
show version | include VersionVerify Fix Applied:
After upgrade, run 'show version' to confirm version 7.6.0 or higher and monitor Snort process stability.📡 Detection & Monitoring
Log Indicators:
- Repeated Snort process restarts in system logs
- Watchdog timeout messages
- High CPU usage alerts from Snort
Network Indicators:
- Unusual traffic patterns with malformed packets
- Increased latency or packet drops through firewall
SIEM Query:
source="ftd_logs" AND ("Snort restart" OR "watchdog" OR "infinite loop")