CVE-2020-3488
📋 TL;DR
This vulnerability allows an unauthenticated attacker on the same network segment to send specially crafted CAPWAP packets to Cisco Catalyst 9800 Series Wireless Controllers running vulnerable IOS XE software, causing the device to crash and reload. This results in a denial of service (DoS) condition that disrupts wireless network operations. Organizations using affected Cisco wireless controllers are at risk.
💻 Affected Systems
- Cisco Catalyst 9800 Series Wireless Controllers
📦 What is this software?
Ios Xe by Cisco
Cisco IOS XE is Cisco's modern network operating system running on enterprise routers, switches, and wireless controllers deployed across corporate networks, data centers, branch offices, and service provider infrastructure worldwide. As the evolution of Cisco IOS, IOS XE provides a Linux-based modu...
Learn more about Ios Xe →⚠️ Risk & Real-World Impact
Worst Case
Complete wireless network outage affecting all connected devices and services until the controller reboots, potentially causing business disruption and service level agreement violations.
Likely Case
Temporary wireless service disruption affecting users and devices until automatic controller reboot completes, typically lasting several minutes.
If Mitigated
Minimal impact with proper network segmentation and monitoring, allowing quick detection and isolation of attack traffic.
🎯 Exploit Status
Exploitation requires network adjacency but no authentication, making it relatively easy for attackers with network access. The vulnerability is in protocol parsing, which typically requires minimal technical skill to exploit.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Cisco IOS XE Software releases 16.12.4, 17.3.3, 17.6.1 or later
Vendor Advisory: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-capwap-dos-TPdNTdyq
Restart Required: Yes
Instructions:
1. Download the fixed software version from Cisco Software Center. 2. Backup current configuration. 3. Upgrade to fixed release using standard IOS XE upgrade procedures. 4. Reboot the controller to load new software.
🔧 Temporary Workarounds
Network Segmentation
allRestrict CAPWAP traffic to trusted network segments only, preventing unauthorized devices from sending CAPWAP packets to controllers.
access-list 100 permit udp host <trusted-ap-ip> host <controller-ip> eq 5246
access-list 100 permit udp host <trusted-ap-ip> host <controller-ip> eq 5247
access-list 100 deny udp any any eq 5246
access-list 100 deny udp any any eq 5247
interface <controller-interface>
ip access-group 100 in
🧯 If You Can't Patch
- Implement strict network access controls to limit which devices can communicate with wireless controllers on CAPWAP ports (5246-5247).
- Deploy intrusion prevention systems (IPS) or network monitoring to detect and block malformed CAPWAP packets.
🔍 How to Verify
Check if Vulnerable:
Check IOS XE version with 'show version' command. If running releases earlier than 16.12.4, 17.3.3, or 17.6.1, the device is vulnerable.Check Version:
show version | include VersionVerify Fix Applied:
After upgrade, verify version with 'show version' command confirms running 16.12.4, 17.3.3, 17.6.1 or later.📡 Detection & Monitoring
Log Indicators:
- Controller crash and reload events in system logs
- Unexpected CAPWAP protocol errors or malformed packet warnings
Network Indicators:
- Unusual CAPWAP traffic from non-AP sources
- Multiple malformed CAPWAP packets to controller IPs
SIEM Query:
source="cisco_wlc" AND (event_type="crash" OR event_type="reload" OR message="*CAPWAP*malformed*")