CVE-2019-16019
📋 TL;DR
This vulnerability in Cisco IOS XR Software allows remote attackers to cause denial of service by sending specially crafted BGP EVPN update messages. The BGP process restarts unexpectedly when processing these malformed attributes, disrupting network routing. Only systems with BGP EVPN functionality enabled and configured with BGP peers are affected.
💻 Affected Systems
- Cisco IOS XR Software
📦 What is this software?
Ios Xr by Cisco
Ios Xr by Cisco
Ios Xr by Cisco
Ios Xr by Cisco
⚠️ Risk & Real-World Impact
Worst Case
Complete BGP routing disruption causing network-wide outages, loss of connectivity, and cascading failures across interconnected networks.
Likely Case
Intermittent BGP process restarts leading to routing instability, packet loss, and degraded network performance until manual intervention.
If Mitigated
Limited impact with proper BGP peer filtering and network segmentation, potentially causing only localized routing issues.
🎯 Exploit Status
Exploitation requires sending crafted BGP EVPN update messages from a configured BGP peer or injecting into existing BGP TCP sessions. Attacker needs network access to BGP peer connections.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 6.6.3, 7.0.1, 7.1.1 or later
Vendor Advisory: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20200122-ios-xr-evpn
Restart Required: Yes
Instructions:
1. Check current IOS XR version. 2. Download appropriate fixed release from Cisco Software Center. 3. Follow Cisco IOS XR upgrade procedures. 4. Reload the device to apply the update.
🔧 Temporary Workarounds
BGP Peer Filtering
allImplement strict BGP peer filtering to only accept connections from trusted, known peers using BGP session protection mechanisms.
router bgp <AS>
neighbor <IP> password <password>
neighbor <IP> ttl-security hops <hops>
neighbor <IP> transport connection-mode passive
BGP Session Protection
allEnable BGP TCP MD5 authentication and TTL security to prevent unauthorized BGP session establishment.
router bgp <AS>
neighbor <IP> password <md5-password>
neighbor <IP> ttl-security hops <hops>
🧯 If You Can't Patch
- Implement strict BGP peer filtering and authentication using MD5 or TCP-AO
- Deploy network monitoring to detect anomalous BGP update patterns and restart events
🔍 How to Verify
Check if Vulnerable:
Check IOS XR version with 'show version' and compare against vulnerable releases (prior to 6.6.3, 7.0.1, 7.1.1). Verify BGP EVPN configuration with 'show running-config router bgp'.Check Version:
show version | include Cisco IOS XR SoftwareVerify Fix Applied:
After upgrade, confirm version is 6.6.3, 7.0.1, 7.1.1 or later using 'show version'. Monitor BGP process stability with 'show processes bgp'.📡 Detection & Monitoring
Log Indicators:
- BGP process restart messages in system logs
- Unexpected BGP neighbor state changes
- EVPN route processing errors
Network Indicators:
- Unusual BGP update patterns from peers
- BGP session resets
- Routing table instability
SIEM Query:
source="ios-xr" AND ("BGP.*restart" OR "EVPN.*error" OR "BGP.*process.*died")