CVE-2021-34696 Explained : Impact and Mitigation

A vulnerability in the access control list (ACL) programming of Cisco ASR 900 and ASR 920 Series Aggregation Services Routers could allow an unauthenticated, remote attacker to bypass a configured ACL. This CVE was published on September 22, 2021, by Cisco.

Understanding CVE-2021-34696

This section delves into the details of the vulnerability, its impact, technical aspects, and mitigation strategies.

What is CVE-2021-34696?

The vulnerability in the ACL programming of Cisco ASR 900 and ASR 920 Series Routers allows a remote attacker to bypass a configured ACL due to incorrect hardware programming.

The Impact of CVE-2021-34696

The vulnerability poses a medium severity threat, allowing attackers to bypass ACLs and potentially gain unauthorized access to affected devices.

Technical Details of CVE-2021-34696

This section provides detailed technical information about the vulnerability.

Vulnerability Description

The flaw arises from incorrect hardware programming when ACLs are configured using methods other than the CLI, enabling attackers to bypass configured ACLs.

Affected Systems and Versions

The vulnerability impacts Cisco IOS XE Software in ASR 900 and ASR 920 Series Routers.

Exploitation Mechanism

By sending traffic through the affected device, an attacker could exploit the vulnerability to bypass the configured ACL.

Mitigation and Prevention

Here are steps to mitigate and prevent the exploitation of CVE-2021-34696.

Immediate Steps to Take

It is recommended to apply the latest security patches provided by Cisco to address this vulnerability.

Long-Term Security Practices

Ensure ACL configurations are done using the CLI and regularly update and patch networking devices.

Patching and Updates

Regularly check for security advisories from Cisco and apply patches promptly to secure your network.