CVE-2025-20146

Remediation / Mitigation Strategy for CVE-2025-20146

This document outlines a remediation and mitigation strategy for CVE-2025-20146, a vulnerability affecting Cisco IOS XR Software running on Cisco ASR 9000, ASR 9902, and ASR 9903 Series Routers.

1. Vulnerability Description:

  • Vulnerability: Cisco IOS XR Software vulnerability related to the handling of malformed IPv4 multicast packets. This affects line cards where the interface has either an IPv4 access control list (ACL) or a QoS policy applied.
  • Affected Products: Cisco ASR 9000 Series Aggregation Services Routers, ASR 9902 Compact High-Performance Routers, and ASR 9903 Compact High-Performance Routers running affected versions of Cisco IOS XR Software.
  • Root Cause: The vulnerability is due to the incorrect handling of malformed IPv4 multicast packets received by line cards with IPv4 ACLs or QoS policies.
  • Attack Vector: Remote, unauthenticated attacker.
  • Impact: Denial of Service (DoS). An attacker can cause a line card to reset, disrupting traffic flow over that line card. This results in temporary loss of connectivity for affected services and users.

2. Severity:

  • CVSS Score: 8.6 (High)
  • CVSS Vector: (Calculated based on values provided: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H) This CVSS vector indicates the following characteristics:
    • AV:N (Network): The vulnerability is exploitable over the network.
    • AC:L (Low): Exploitation requires little or no special access or circumstances.
    • PR:N (None): No privileges are required to perform the attack.
    • UI:N (None): No user interaction is required.
    • S:C (Changed): The vulnerability affects a component beyond the attacker’s control.
    • C:N (None): There is no loss of confidentiality.
    • I:N (None): There is no loss of integrity.
    • A:H (High): There is a high impact on availability.
  • Severity Level: High

3. Known Exploit:

  • As of the information provided, a specific, publicly available exploit is not explicitly mentioned. However, the description clearly outlines the method: crafting and sending malformed IPv4 multicast packets. Therefore, the potential for exploit is high, and proactive remediation is critical. Given the CVSS score, it’s likely that proof-of-concept exploits will emerge quickly once the vulnerability is made public.

4. Remediation Strategy:

  • Immediate Action (Mitigation):
    • Rate Limiting Multicast Traffic: Implement rate limiting on multicast traffic entering the affected interfaces. This can help to reduce the impact of a potential attack by limiting the number of malicious packets that can reach the vulnerable component. Carefully consider legitimate multicast traffic requirements before implementing aggressive rate limiting.
    • Monitor for Anomalous Multicast Traffic: Monitor network traffic for unusual patterns or spikes in multicast traffic, especially from unexpected sources. Use NetFlow, sFlow, or similar network monitoring tools to identify potential attacks.
    • Disable Unnecessary Multicast Routing: If multicast routing is not required on specific interfaces, disable it. This reduces the attack surface.
  • Long-Term Solution (Remediation):
    • Apply Cisco Patches/Upgrades: The primary and recommended solution is to apply the appropriate Cisco IOS XR Software patch or upgrade to a version that addresses CVE-2025-20146. Cisco will release a software update that fixes the vulnerability. Monitor Cisco security advisories and promptly apply the fix when available. This is the most important step. Refer to Cisco’s official advisory for the specific affected versions and the corresponding fixed versions.
    • Review and Harden ACLs: While ACLs are part of the problem trigger, ensure that ACLs on affected interfaces are properly configured. Although not a direct fix, well-configured ACLs can help to filter potentially malicious traffic.
    • Evaluate QoS Policies: Review QoS policies applied to affected interfaces. While not a direct fix, ensure they are configured correctly and not contributing to the vulnerability’s exploitability.
  • Verification:
    • Testing After Patching: After applying the patch or upgrade, thoroughly test the affected routers to ensure that the vulnerability is resolved and that there are no new issues introduced. This should be done in a lab environment before deploying to production.
    • Penetration Testing: Consider conducting penetration testing to validate the effectiveness of the remediation and identify any remaining vulnerabilities.

5. Communication Plan:

  • Internal Communication: Inform network administrators, security teams, and other relevant personnel about the vulnerability and the remediation plan.
  • Stakeholder Communication: Communicate with key stakeholders (e.g., management, customers) about the potential impact of the vulnerability and the steps being taken to address it.

6. Timeline:

  • Immediate: Implement mitigation strategies (rate limiting, monitoring).
  • As Soon As Possible: Identify affected devices and plan for patching. Monitor Cisco for patch availability.
  • Within [Specific Timeframe - e.g., 7 days of patch release]: Apply Cisco patches/upgrades to affected devices in a controlled manner (lab testing first).
  • Ongoing: Continue monitoring network traffic and reviewing security configurations.

7. Resources:

  • Cisco Security Advisories: Monitor Cisco’s official security advisories page for updates on this vulnerability and other security issues.
  • Cisco TAC (Technical Assistance Center): Contact Cisco TAC for assistance with patching, upgrading, or troubleshooting.

Important Considerations:

  • Downtime: Patching and upgrading Cisco routers may require downtime. Plan maintenance windows accordingly.
  • Compatibility: Ensure that the chosen patch or upgrade is compatible with your existing network configuration and other software components.
  • Rollback Plan: Have a rollback plan in place in case the patching or upgrade process fails.
  • Vendor Advisory: Always refer to the official Cisco security advisory for the most accurate and up-to-date information. The information above is based solely on the provided text and should be supplemented with official Cisco documentation.

Assigner

Date

  • Published Date: 2025-03-12 16:15:22
  • Updated Date: 2025-03-12 16:15:22

More Details

CVE-2025-20146