CVE-2020-3351
📋 TL;DR
An unauthenticated remote attacker can send crafted UDP messages to Cisco SD-WAN devices, causing a denial of service (DoS) by exploiting improper validation in peering messages. This affects organizations using vulnerable Cisco SD-WAN Solution Software, potentially disrupting network services and dependent devices.
💻 Affected Systems
- Cisco SD-WAN Solution Software
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete device failure leading to widespread network outage and service disruption across the SD-WAN infrastructure.
Likely Case
Targeted device becomes unresponsive, causing localized DoS and impacting network performance for connected systems.
If Mitigated
Minimal impact if patched or workarounds applied, with potential for brief service interruptions during exploitation attempts.
🎯 Exploit Status
Exploitation involves sending crafted UDP packets, which is relatively straightforward for attackers with network access.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Refer to Cisco advisory for specific fixed versions (e.g., updates released in response to CVE-2020-3351).
Vendor Advisory: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-sdw-dos-KWOdyHnB
Restart Required: Yes
Instructions:
1. Review the Cisco advisory for affected versions. 2. Download and apply the recommended software update from Cisco. 3. Restart the SD-WAN device to implement the patch. 4. Verify the fix using version checks and monitoring.
🔧 Temporary Workarounds
Network Segmentation and Access Control
allRestrict UDP traffic to SD-WAN peering ports from trusted sources only to block exploit attempts.
Configure firewall rules to allow UDP peering messages only from authorized IP addresses.
🧯 If You Can't Patch
- Implement strict network access controls to limit UDP traffic to SD-WAN devices from trusted networks.
- Monitor network logs for unusual UDP packet patterns and set up alerts for potential exploitation attempts.
🔍 How to Verify
Check if Vulnerable:
Check the software version on Cisco SD-WAN devices against the affected versions listed in the Cisco advisory.Check Version:
Use Cisco CLI commands such as 'show version' or 'show software' on the SD-WAN device to check the current software version.Verify Fix Applied:
After patching, confirm the device is running a fixed version and monitor for DoS symptoms or abnormal UDP traffic.📡 Detection & Monitoring
Log Indicators:
- Log entries showing service failures, crashes, or abnormal UDP packet processing on SD-WAN devices.
Network Indicators:
- Unusual spikes in UDP traffic to SD-WAN peering ports, especially from untrusted sources.
SIEM Query:
Example: search for UDP packets with abnormal payloads or high volume targeting SD-WAN device IPs on peering ports.