CVE-2022-20767
📋 TL;DR
This vulnerability allows unauthenticated remote attackers to cause denial of service on Cisco Firepower Threat Defense devices by sending crafted UDP packets that trigger improper DNS reputation rule handling. Only affects FTD devices running Snort 3, causing traffic to be dropped through the affected device.
💻 Affected Systems
- Cisco Firepower Threat Defense (FTD) Software
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete network outage through the affected FTD device, dropping all traffic and requiring device reboot to restore functionality.
Likely Case
Intermittent traffic drops and performance degradation affecting network connectivity through the device.
If Mitigated
Minimal impact with proper network segmentation and monitoring in place to detect and respond to attack attempts.
🎯 Exploit Status
Exploitation requires sending crafted UDP packets, which is relatively straightforward for attackers with network access.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Cisco FTD Software versions 7.0.1 and later, 6.7.0.3 and later, 6.6.5.2 and later
Vendor Advisory: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-FTD-snort3-DOS-Aq38LVdM
Restart Required: Yes
Instructions:
1. Download appropriate patch from Cisco Software Center. 2. Upload to FTD device. 3. Install update via CLI or FMC. 4. Reboot device after installation.
🔧 Temporary Workarounds
Disable DNS reputation enforcement rule
allTemporarily disable the vulnerable DNS reputation rule to prevent exploitation
configure terminal
no dns-reputation enable
Rate limit UDP connections
allImplement UDP connection rate limiting to prevent connection buildup
class-map match-any UDP-TRAFFIC
match protocol udp
policy-map UDP-POLICY
class UDP-TRAFFIC
police cir 1000000
🧯 If You Can't Patch
- Implement network segmentation to isolate FTD devices from untrusted networks
- Deploy intrusion prevention systems to detect and block crafted UDP packet attacks
🔍 How to Verify
Check if Vulnerable:
Check FTD version and Snort version: 'show version' and verify if running Snort 3Check Version:
show version | include VersionVerify Fix Applied:
Verify installed version is patched: 'show version' should show 7.0.1+, 6.7.0.3+, or 6.6.5.2+📡 Detection & Monitoring
Log Indicators:
- High UDP connection counts
- Snort process crashes or restarts
- DNS reputation rule errors
Network Indicators:
- Unusual UDP traffic patterns
- Spike in DNS queries through FTD
- Network performance degradation
SIEM Query:
source="ftd_logs" AND ("UDP connection limit" OR "Snort restart" OR "DNS reputation error")