CVE-2020-3369
📋 TL;DR
An unauthenticated remote attacker can cause Cisco SD-WAN vEdge Routers to reboot continuously by sending crafted FTP packets through the device's deep packet inspection engine. This creates a denial-of-service condition affecting network availability. All organizations using vulnerable Cisco SD-WAN vEdge Routers are affected.
💻 Affected Systems
- Cisco SD-WAN vEdge Routers
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Continuous device reboots causing complete network outage for all traffic passing through affected routers, potentially affecting entire network segments.
Likely Case
Intermittent network disruptions and service degradation as devices reboot, impacting business operations and connectivity.
If Mitigated
Minimal impact with proper network segmentation and monitoring allowing quick detection and isolation of affected devices.
🎯 Exploit Status
Exploitation requires sending crafted FTP packets through the device, which is relatively straightforward for attackers with network access.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Cisco SD-WAN vEdge Router Software Release 20.3.1 and later
Vendor Advisory: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-fpdos-hORBfd9f
Restart Required: Yes
Instructions:
1. Download the fixed software from Cisco Software Center. 2. Upload to vManage. 3. Create software upgrade policy. 4. Apply policy to affected devices. 5. Reboot devices after upgrade.
🔧 Temporary Workarounds
Disable DPI for FTP traffic
allConfigure DPI policies to exclude FTP traffic from inspection
vEdge(config)# policy dpi-policy
vEdge(config-dpi-policy)# no match ftp
Block FTP traffic at network perimeter
allUse firewall rules to block FTP traffic from untrusted sources
🧯 If You Can't Patch
- Implement network segmentation to isolate vEdge routers from untrusted networks
- Deploy intrusion prevention systems to detect and block crafted FTP packets
🔍 How to Verify
Check if Vulnerable:
Check device version via vManage or CLI: show version | include SoftwareCheck Version:
show version | include SoftwareVerify Fix Applied:
Verify software version is 20.3.1 or later and check system stability after applying fix📡 Detection & Monitoring
Log Indicators:
- Repeated device reboots
- FTP traffic anomalies
- DPI engine crash logs
Network Indicators:
- Unusual FTP traffic patterns
- Device unreachable alerts
- Increased reboot events
SIEM Query:
source="vedge" AND (event="reboot" OR event="crash") AND protocol="FTP"