CVE-2023-20187 : Vulnerability Insights and Analysis

A vulnerability in the Multicast Leaf Recycle Elimination (mLRE) feature of Cisco IOS XE Software for Cisco ASR 1000 Series Aggregation Services Routers could allow an unauthenticated, remote attacker to cause the affected device to reload, resulting in a denial of service (DoS) condition.

Understanding CVE-2023-20187

This section delves into the details of CVE-2023-20187, its impact, technical description, affected systems, exploitation mechanism, mitigation steps, and prevention measures.

What is CVE-2023-20187?

CVE-2023-20187 is a vulnerability found in the Multicast Leaf Recycle Elimination (mLRE) feature of Cisco IOS XE Software utilized in Cisco ASR 1000 Series Aggregation Services Routers. The vulnerability could be exploited by an attacker to trigger a device reload, leading to a denial of service (DoS) situation.

The Impact of CVE-2023-20187

The vulnerability in Cisco IOS XE Software could permit a remote, unauthenticated attacker to send malicious IPv6 multicast packets, causing the affected device to reload. This could result in a disruption of service, impacting the availability of the device.

Technical Details of CVE-2023-20187

The technical aspects of CVE-2023-20187 include its vulnerability description, affected systems, affected versions, and the exploitation mechanism.

Vulnerability Description

The vulnerability stems from the improper handling of specific IPv6 multicast packets in Cisco IOS XE Software. When these packets are fanned out more than seven times on an affected device, it triggers the vulnerability. An attacker could exploit this by sending a particular IPv6 multicast or IPv6 multicast VPN (MVPNv6) packet, leading to a device reload and subsequent DoS.

Affected Systems and Versions

Cisco IOS XE Software versions ranging from 3.7.1S to 17.11.1a are impacted by this vulnerability, affecting a wide range of products within the Cisco ASR 1000 Series.

Exploitation Mechanism

The vulnerability can be exploited by sending a specific IPv6 multicast or IPv6 multicast VPN (MVPNv6) packet through the affected device. Successful exploitation results in reloading the device and causing a denial of service.

Mitigation and Prevention

To address CVE-2023-20187, immediate steps should be taken, and long-term security practices should be implemented to enhance system resilience.

Immediate Steps to Take

It is crucial to apply the necessary patches and updates provided by Cisco to mitigate the vulnerability. Network administrators should also monitor and restrict the network traffic to prevent exploitation.

Long-Term Security Practices

Implementing network segmentation, access controls, and regular security assessments can help strengthen the overall security posture of the network and devices. Continuous monitoring for suspicious activities is essential.

Patching and Updates

Cisco has released patches and updates to address CVE-2023-20187. It is recommended to apply these fixes promptly to safeguard the affected systems from potential exploitation.

Reference: Cisco Security Advisory for CVE-2023-20187