Network operators beware. Cisco’s latest high-severity vulnerability has the potential to wreak havoc on your infrastructure. The bug (CVE-2025-20115) affects IOS XR routers and can crash the BGP process with just one malicious update message. Yeah, you read that right – one message.
Disclosed on March 12, 2025, this nasty flaw scored an 8.6 on the CVSS scale. It’s no joke. The vulnerability stems from improper handling of AS_CONFED_SEQUENCE attributes containing 255 or more AS numbers, causing a buffer overflow that corrupts memory. When triggered, the BGP process simply dies. Tough luck for your network stability.
The bug impacts several carrier-grade router lines including Network Convergence System (NCS), Carrier Routing System (CRS), and ASR 9000 series. But there’s a catch – your system needs BGP confederation enabled to be vulnerable. Small comfort, right?
Exploitation doesn’t require authentication or direct adjacency to the target. Attackers just need control of a BGP confederation speaker in the same autonomous system. They send a crafted BGP update and boom – your routing process crashes. The memory usage will spike dramatically to 90% utilization just before failure occurs. The resulting outage can disrupt inter-domain routing, interrupt traffic flow, and compromise overall network reliability.
Affected software includes IOS XR versions 7.11 and earlier, 24.1 and earlier, and 24.2 up to 24.2.20. Version 24.4 remains unaffected. Cisco has released patches. Apply them now.
While waiting for updates, network admins can implement temporary mitigations. Filter BGP updates with excessively long AS paths. Implement BGP peer authentication. Monitor for abnormal BGP behavior. The BGP session resets often produce distinctive log message patterns that can help identify when you’re under attack. These steps might save your bacon.
Long-term security requires regular audits of BGP configurations and implementation of routing security protocols like RPKI and BGPsec where feasible. Network segmentation limits the blast radius of potential BGP issues. A proper risk assessment framework can help identify your most vulnerable assets and prioritize defensive measures against this type of threat.
The vulnerability hasn’t been exploited in the wild yet. But why take chances? Your network’s stability depends on addressing this flaw. Now.
