CVE-2025-20209
📋 TL;DR
An unauthenticated remote attacker can send malformed IKEv2 packets to Cisco IOS XR devices, causing them to stop processing all control plane UDP packets. This results in a denial of service condition affecting VPN and routing functionality. Only Cisco IOS XR software with IKEv2 enabled is affected.
💻 Affected Systems
- Cisco IOS XR Software
📦 What is this software?
Ios Xr by Cisco
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⚠️ Risk & Real-World Impact
Worst Case
Complete loss of control plane UDP processing, disrupting VPN tunnels, routing protocols (BGP, OSPF), and other UDP-based management services, requiring device reboot.
Likely Case
Targeted DoS attacks against specific devices causing VPN outages and routing instability until packets stop or device is restarted.
If Mitigated
If patched, no impact. If unpatched but behind firewalls with IKEv2 filtering, limited exposure.
🎯 Exploit Status
Exploitation requires crafting specific malformed IKEv2 packets. No authentication needed.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check Cisco advisory for specific fixed versions
Vendor Advisory: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-xrike-9wYGpRGq
Restart Required: No
Instructions:
1. Check Cisco advisory for affected versions. 2. Download and install appropriate fixed software version. 3. No restart required according to advisory.
🔧 Temporary Workarounds
No workarounds available
allCisco states there are no workarounds for this vulnerability
🧯 If You Can't Patch
- Implement network ACLs to block IKEv2 traffic (UDP port 500 and 4500) from untrusted sources
- Monitor for IKEv2 traffic anomalies and implement rate limiting on IKEv2 packets
🔍 How to Verify
Check if Vulnerable:
Check Cisco advisory for affected IOS XR versions and compare to your device versionCheck Version:
show version | include Cisco IOS XRVerify Fix Applied:
Verify installed version matches or exceeds fixed version listed in Cisco advisory📡 Detection & Monitoring
Log Indicators:
- Sudden increase in IKEv2 packet processing errors
- Control plane UDP service failures
- VPN tunnel establishment failures
Network Indicators:
- Unusual IKEv2 traffic patterns to network devices
- Spike in malformed IKEv2 packets
SIEM Query:
source_interface:network_device AND (protocol:UDP AND (port:500 OR port:4500)) AND packet_size:anomalous