CVE-2025-20115
📋 TL;DR
A memory corruption vulnerability in Cisco IOS XR's BGP confederation implementation allows unauthenticated remote attackers to cause denial of service. Attackers can exploit this by sending crafted BGP updates with AS_CONFED_SEQUENCE attributes containing 255+ AS numbers, causing the BGP process to restart. This affects networks using BGP confederations with vulnerable Cisco IOS XR devices.
💻 Affected Systems
- Cisco IOS XR Software
📦 What is this software?
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⚠️ Risk & Real-World Impact
Worst Case
Complete BGP session disruption leading to network-wide routing instability and extended outage until process recovery or manual intervention.
Likely Case
Intermittent BGP process restarts causing temporary routing flaps and packet loss during convergence periods.
If Mitigated
Limited to isolated BGP speaker restarts with minimal impact if proper network segmentation and redundancy exist.
🎯 Exploit Status
Exploitation requires BGP peer access and knowledge of BGP confederation configuration. Attackers need to control a BGP speaker within the same autonomous system confederation.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Refer to Cisco Security Advisory for specific fixed releases
Vendor Advisory: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-iosxr-bgp-dos-O7stePhX
Restart Required: No
Instructions:
1. Review Cisco Security Advisory for specific fixed releases. 2. Schedule maintenance window. 3. Download and apply appropriate IOS XR software update. 4. Verify BGP sessions remain stable post-update.
🔧 Temporary Workarounds
BGP Confederation Filtering
Cisco IOS XRImplement inbound route filtering to reject BGP updates containing AS_CONFED_SEQUENCE attributes with 255+ AS numbers
router bgp <as-number>
neighbor <ip-address> route-map FILTER-AS-CONFED in
route-map FILTER-AS-CONFED deny 10
match as-path 100
route-map FILTER-AS-CONFED permit 20
ip as-path access-list 100 permit _65535_
🧯 If You Can't Patch
- Implement strict BGP peer authentication using MD5 or TCP-AO to prevent unauthorized BGP updates
- Deploy network segmentation to isolate BGP confederation speakers and limit blast radius
🔍 How to Verify
Check if Vulnerable:
Check IOS XR version and BGP confederation configuration: show version | include Version, show running-config router bgpCheck Version:
show version | include Cisco IOS XR SoftwareVerify Fix Applied:
Verify updated IOS XR version and monitor BGP process stability: show version, show processes bgp | include State📡 Detection & Monitoring
Log Indicators:
- BGP process restart messages
- Memory corruption errors in system logs
- Unexpected BGP neighbor state changes
Network Indicators:
- Sudden BGP route withdrawals
- Increased BGP update traffic with large AS paths
- Routing table instability
SIEM Query:
source="iosxr" AND ("BGP.*restart" OR "memory corruption" OR "%BGP-5-ADJCHANGE")