Mitigating CVE-2025-20115: Cisco IOS XR BGP Confederation DoS Vulnerability

Executive Summary

The Cisco IOS XR Software Border Gateway Protocol (BGP) Confederation Denial of Service vulnerability, identified as CVE-2025-20115, presents a critical challenge for network security. With a CVSS Score of 8.6, this vulnerability affects devices running Cisco IOS XR configured with BGP confederation. It arises from a memory corruption flaw that could be exploited by unauthenticated attackers, leading to a Denial of Service (DoS). Understanding the technical intricacies of this vulnerability and implementing robust mitigation strategies is imperative for safeguarding network integrity.

Technical Information

The Cisco IOS XR BGP Confederation DoS Vulnerability is rooted in the improper handling of the AS_CONFED_SEQUENCE attribute within BGP update messages. Specifically, the vulnerability is due to a memory corruption issue where an attacker can inject a crafted message containing 255 or more autonomous system numbers. This overload leads to process instability and potentially forces a BGP process restart, disrupting network operations.

This vulnerability is cataloged under CWE-120, which indicates a buffer copy without adequate input size checking. The threat is pronounced in environments where BGP confederations are prevalent, as attackers can exploit this flaw to degrade network performance and availability.

The vulnerability is documented under Advisory ID: cisco-sa-iosxr-bgp-dos-O7stePhX and tracked by Bug ID: CSCwk15887. It is crucial to note that while the Cisco Security Advisory identifies potential attack vectors, the actual exploitation in the wild has not been reported as of this document's release.

The affected software versions include Cisco IOS XR Release 7.11 and earlier, Release 24.1 and earlier, Release 24.2 until version 24.2.21, and Release 24.3, which has been patched in version 24.3.1. Release 24.4 remains unaffected, alongside other Cisco software such as IOS, IOS XE, and NX-OS.

Exploitation in the Wild

Currently, there is no evidence of active exploitation of this vulnerability in the wild. However, the public discourse surrounding the announcement titled "Crafting endless AS-PATHS in BGP" has brought attention to the potential threats. Organizations should remain vigilant and proactive in applying mitigations to prevent any future exploitation.

APT Groups using this vulnerability

While specific APT groups have not been identified exploiting this vulnerability, entities operating in sectors with high stakes in network availability should be particularly cautious. The lack of known exploitation should not diminish the urgency of addressing this vulnerability, given the high CVSS score and potential impact.

Affected Product Versions

The vulnerability impacts the following versions of Cisco IOS XR Software:

• Release 7.11 and earlier
• Release 24.1 and earlier
• Release 24.2 up to version 24.2.21
• Release 24.3 before version 24.3.1

It is essential to upgrade to the latest fixed releases to mitigate potential risks.

Workaround and Mitigation

To mitigate the risk of exploitation, Cisco recommends configuring a routing policy to limit the AS_CONFED_SEQUENCE attribute to 254 or fewer AS numbers. The policy can be implemented as follows:

plaintext route-policy max-asns if as-path length ge 254 then drop else pass endif end-policy

In addition to this workaround, it is highly recommended to upgrade to the latest software releases where the vulnerability has been addressed. Regularly monitoring network traffic and implementing security best practices can further enhance protection against potential threats.

References

For more detailed information and technical guidance, please refer to the following resources:

1. Cisco Security Advisory: Cisco IOS XR Software Border Gateway Protocol Confederation Denial of Service Vulnerability https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-iosxr-bgp-dos-O7stePhX
2. Public Announcement: Crafting endless AS-PATHS in BGP.

Rescana is here for you

At Rescana, we understand the complexities of managing cybersecurity risks. Our Third Party Risk Management (TPRM) platform provides comprehensive solutions to help you identify, assess, and mitigate potential vulnerabilities in your network infrastructure. We are committed to supporting our clients in navigating the ever-evolving cybersecurity landscape. If you have any questions about this report or other cybersecurity concerns, please contact us at ops@rescana.com.