CVE-2021-1513
📋 TL;DR
This vulnerability in Cisco SD-WAN Software allows unauthenticated remote attackers to cause affected devices to reload by sending malformed packets, resulting in denial of service. It affects Cisco SD-WAN vEdge routers and vSmart controllers running vulnerable software versions. The vulnerability stems from insufficient input validation in the vDaemon process.
💻 Affected Systems
- Cisco SD-WAN vEdge Routers
- Cisco SD-WAN vSmart Controllers
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete service disruption across SD-WAN network as multiple devices reload simultaneously, causing extended downtime and potential data loss during failover.
Likely Case
Intermittent device reloads causing temporary network outages and degraded performance until devices restart and re-establish connections.
If Mitigated
Minimal impact with proper network segmentation and monitoring, allowing quick detection and isolation of affected devices.
🎯 Exploit Status
Crafting malformed packets requires moderate networking knowledge but no authentication, making exploitation relatively straightforward for determined attackers.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 20.3.4, 20.4.1, or 20.5.1 and later
Vendor Advisory: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-sdwan-dos-Ckn5cVqW
Restart Required: Yes
Instructions:
1. Download appropriate fixed version from Cisco Software Center. 2. Backup current configuration. 3. Upgrade to 20.3.4, 20.4.1, or 20.5.1 or later. 4. Verify upgrade completion and functionality.
🔧 Temporary Workarounds
Network Segmentation
allRestrict access to SD-WAN management interfaces to trusted networks only
Configure ACLs to limit traffic to vDaemon ports from authorized sources only
Rate Limiting
allImplement rate limiting on control plane traffic to reduce impact
Configure QoS policies to limit traffic to vDaemon process
🧯 If You Can't Patch
- Implement strict network access controls to limit exposure to trusted sources only
- Deploy intrusion detection/prevention systems to monitor for malformed packet patterns
🔍 How to Verify
Check if Vulnerable:
Check software version via CLI: show version | include SoftwareCheck Version:
show version | include SoftwareVerify Fix Applied:
Verify version is 20.3.4, 20.4.1, 20.5.1 or later and monitor for device stability📡 Detection & Monitoring
Log Indicators:
- Unexpected device reloads
- vDaemon process crashes
- High CPU/memory usage before reload
Network Indicators:
- Unusual traffic patterns to vDaemon ports
- Malformed packet detection
- Sudden loss of control plane connectivity
SIEM Query:
source="cisco-sdwan" AND (event_type="crash" OR event_type="reload") AND process="vDaemon"