CVE-2025-20142
Vulnerability Remediation / Mitigation Strategy: CVE-2025-20142
Vulnerability Description:
CVE-2025-20142 is a vulnerability affecting Cisco IOS XR Software running on Cisco ASR 9000 Series, ASR 9902, and ASR 9903 routers. Specifically, it relates to the improper handling of malformed IPv4 packets when IPv4 Access Control Lists (ACLs) or Quality of Service (QoS) policies are applied to interfaces on these devices. An attacker can trigger this vulnerability by sending specially crafted IPv4 packets through an affected device. This leads to network processor errors, resulting in a line card reset and a denial-of-service (DoS) condition. Traffic traversing the affected line card will be interrupted until the line card reloads.
The vulnerability is primarily observed in Layer 2 VPN (L2VPN) environments with IPv4 ACLs or QoS applied to bridge virtual interfaces, but Layer 3 configurations with IPv4 ACLs/QoS are also susceptible.
Severity:
- CVSS Score: 8.6 (High)
- CVSS Vector: (Based on the information provided, we can infer a possible CVSS vector. A more complete vector would be ideal, but we can assume a plausible scenario): AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- Impact: Denial of Service (DoS) - Line card reset/shutdown, leading to traffic loss.
Known Exploit:
- An attacker can exploit this vulnerability by sending crafted IPv4 packets to an affected device, specifically targeting interfaces where IPv4 ACLs or QoS policies are configured. The type of “crafting” is not described.
Remediation / Mitigation Strategy:
The primary goal is to prevent the crafted IPv4 packets from triggering the vulnerability and causing line card resets. Given the information provided, a multi-layered approach is recommended:
Identify Affected Devices and Interfaces:
- Inventory all Cisco ASR 9000 Series, ASR 9902, and ASR 9903 routers running Cisco IOS XR.
- For each device, identify all interfaces where IPv4 ACLs or QoS policies are applied. Pay special attention to bridge virtual interfaces in L2VPN environments, as these have been observed to be more susceptible. Use CLI commands like
show running-config interface <interface_name>to inspect configurations. - Determine the version of Cisco IOS XR running on these devices.
Apply Software Updates/Patches (Highest Priority):
- Consult Cisco’s Security Advisory: Search for the official Cisco security advisory for CVE-2025-20142 on the Cisco Security Portal (cisco.com/security). This advisory will provide the definitive list of affected software versions and the recommended fixed versions.
- Upgrade to a Fixed Version: Upgrade the Cisco IOS XR software on affected devices to a fixed version provided by Cisco. Follow Cisco’s upgrade procedures carefully, including planning for maintenance windows and testing in a non-production environment if possible.
Implement Workarounds (If Immediate Patching is Not Possible):
- If immediate patching is not feasible, consider implementing workarounds to mitigate the risk. Important: Workarounds should be considered temporary measures until a proper software update can be applied.
- Rate Limiting/Traffic Shaping: Implement rate limiting or traffic shaping policies on ingress interfaces to limit the rate of IPv4 traffic processed by the affected line cards. This might prevent an attacker from overwhelming the device with crafted packets. This should be tested carefully to ensure legitimate traffic is not impacted.
- Input Filtering: Consider implementing more strict ingress filtering on interfaces where IPv4 ACLs/QoS are already applied. If possible, filter out any packets with characteristics that resemble known exploits for this vulnerability. This approach requires a deeper understanding of the specific packet characteristics that trigger the issue, and should be implemented with caution to avoid blocking legitimate traffic.
- Disable IPv4 ACLs/QoS (Least Desirable): As a last resort, if absolutely necessary, temporarily disable IPv4 ACLs or QoS policies on affected interfaces. This significantly reduces security posture and should only be considered if the risk of exploitation is deemed higher than the risks associated with temporarily disabling these features. Document the reason for disabling these features and create a plan to re-enable them as soon as a software update can be applied.
Monitor and Detect Exploitation Attempts:
- Enable Logging: Ensure that appropriate logging is enabled on affected devices to capture information about potential exploitation attempts. Specifically, enable logging of ACL denies and any error messages related to network processor errors or line card resets.
- Monitor Logs: Regularly monitor the logs for suspicious activity, such as a sudden increase in ACL denies or error messages related to network processor failures.
- Intrusion Detection/Prevention Systems (IDS/IPS): If possible, deploy or update intrusion detection/prevention systems (IDS/IPS) to detect and block packets that match known exploitation patterns for CVE-2025-20142 (if available).
Network Segmentation:
- Implement network segmentation to limit the potential impact of a successful exploit. Isolate critical network segments from less trusted networks.
Security Awareness Training:
- Educate network administrators and security personnel about the vulnerability and the potential risks. Ensure they are aware of the monitoring and detection procedures.
Important Considerations:
- Testing: Thoroughly test any workarounds or software updates in a non-production environment before deploying them to the production network.
- Documentation: Document all implemented remediation and mitigation steps, including the rationale for each action.
- Communication: Communicate the vulnerability and the planned remediation/mitigation steps to stakeholders.
- Stay Informed: Continuously monitor the Cisco Security Portal and other security resources for updates and additional information about CVE-2025-20142.
- CVSS Score Interpretation: The CVSS score should be used as a guideline, but the actual risk to your organization depends on the specific configuration of your network and the criticality of the affected devices.
- Vendor Specific Guidance: Always prioritize the vendor’s official security advisory and follow their recommended remediation steps. This strategy is written using the limited information provided and may be incomplete without the official Cisco Security Advisory.
Assigner
- Cisco Systems, Inc. [email protected]
Date
- Published Date: 2025-03-12 16:15:22
- Updated Date: 2025-03-12 16:15:22