CVE-2025-20115

Remediation / Mitigation Strategy for CVE-2025-20115

This document outlines the remediation and mitigation strategies for CVE-2025-20115, a vulnerability affecting the Border Gateway Protocol (BGP) implementation in Cisco IOS XR Software.

1. Vulnerability Description:

  • Vulnerability: Memory corruption in the BGP confederation implementation.
  • Affected Software: Cisco IOS XR Software
  • Cause: A BGP update with an AS_CONFED_SEQUENCE attribute containing 255 autonomous system numbers (AS numbers) or more can trigger memory corruption.
  • Attack Vector: An unauthenticated, remote attacker can send a crafted BGP update message to a vulnerable device, or a poorly designed network can also lead to the vulnerability being triggered.
  • Impact: Successful exploitation leads to memory corruption, which may cause the BGP process to restart, resulting in a Denial-of-Service (DoS) condition.
  • Conditions for Exploitation:
    • The attacker must control a BGP confederation speaker within the same autonomous system (AS) as the victim.
    • The network can be designed in such a manner that the AS_CONFED_SEQUENCE attribute grows to 255 AS numbers or more

2. Severity:

  • CVSS Score: 8.6 (High)
  • Vector: AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H (Network, Low Attack Complexity, No Privileges Required, No User Interaction, Unchanged Scope, No Confidentiality Impact, No Integrity Impact, High Availability Impact)
  • Severity Level: High. A remote, unauthenticated attacker can trigger a DoS condition with relative ease.

3. Known Exploits:

  • As of the date of this document, details of public exploits specifically targeting CVE-2025-20115 are not readily available. However, the vulnerability description indicates that a crafted BGP update can trigger the vulnerability, suggesting that proof-of-concept exploits are likely possible. Given the high CVSS score, exploitation is considered a serious risk.

4. Remediation Strategy:

  • Apply Patches/Upgrades: The primary and most effective remediation strategy is to upgrade the Cisco IOS XR Software to a version that includes a fix for CVE-2025-20115. Consult the Cisco security advisory for the specific fixed versions:
    • Go to Cisco’s security advisories page (https://sec.cloudapps.cisco.com/security/center/), and search for “CVE-2025-20115”.
    • Follow the instructions provided in the Cisco advisory to download and install the appropriate patch or upgrade.

5. Mitigation Strategy (Until Patching is Possible):

If patching/upgrading is not immediately feasible, implement the following mitigation measures:

  • BGP Route Filtering: Implement strict BGP route filtering policies to limit the size and content of received BGP updates, especially those containing AS_CONFED_SEQUENCE attributes. Specifically, filter routes that may have very large AS_CONFED_SEQUENCE attributes. This is a complex task that requires a deep understanding of your BGP routing policies and your confederation design. Carefully consider the impact of filtering routes on network connectivity and reachability.
  • Confederation Design Review: Review your BGP confederation design to ensure it minimizes the potential for AS_CONFED_SEQUENCE attributes to reach excessive lengths. Consider simplifying your confederation topology or modifying routing policies to prevent long AS_CONFED_SEQUENCE attributes from being propagated. This may require significant network redesign.
  • BGP Peer Monitoring: Implement robust monitoring of BGP peer relationships to detect unexpected or suspicious behavior. Look for frequent BGP session resets, high CPU utilization on BGP-speaking routers, and unexpected changes in the routing table. Alerting on these events can provide early warning of a potential exploitation attempt.
  • Rate Limiting: Implement rate limiting on incoming BGP updates from confederation peers. This will not prevent exploitation, but can reduce the impact of a crafted BGP update by limiting the number of packets processed. Adjust the rate limits according to your network’s normal operating conditions, but avoid setting a value that is too restrictive, as this may impact legitimate BGP operations.
  • Access Control Lists (ACLs): While less effective in this specific scenario, verify that ACLs are in place to restrict access to the BGP-speaking routers to authorized management networks. This reduces the overall attack surface.

6. Testing and Validation:

  • Pre-Production Testing: Before deploying any patches or configuration changes to the production network, thoroughly test them in a controlled pre-production environment to ensure they do not introduce any unintended side effects.
  • Post-Implementation Monitoring: After applying patches or implementing mitigation measures, closely monitor the BGP-speaking routers to verify that the vulnerability has been addressed and that network performance remains stable.

7. Communication and Coordination:

  • Communicate the vulnerability and the implemented remediation/mitigation strategies to all relevant stakeholders, including network engineers, security personnel, and management.
  • Coordinate with upstream and downstream BGP peers to ensure consistency in routing policies and to avoid any routing disruptions during the remediation process.

8. Disclaimer:

This remediation/mitigation strategy is based on the information available at the time of writing. The effectiveness of these measures may vary depending on the specific network environment and the sophistication of the attacker. It is essential to consult the Cisco security advisory for the most up-to-date information and recommendations.

Assigner

Date

  • Published Date: 2025-03-12 16:15:21
  • Updated Date: 2025-03-12 16:15:21

More Details

CVE-2025-20115