CVE-2021-34721 Explained : Impact and Mitigation

Multiple vulnerabilities in the CLI of Cisco IOS XR Software could allow an authenticated, local attacker to gain access to the underlying root shell of an affected device and execute arbitrary commands with root privileges. The Cisco Product Security Incident Response Team (PSIRT) has not detected any public announcements or malicious exploitation of these vulnerabilities.

Understanding CVE-2021-34721

This Common Vulnerabilities and Exposures (CVE) ID refers to vulnerabilities in Cisco IOS XR Software that could be exploited by an authenticated, local attacker to access the root shell and run commands with elevated privileges.

What is CVE-2021-34721?

The CVE-2021-34721 vulnerability involves multiple flaws in the Command Line Interface (CLI) of Cisco IOS XR Software, enabling a local attacker with authentication to access the root shell and execute arbitrary commands as root.

The Impact of CVE-2021-34721

The impact of CVE-2021-34721 is rated as MEDIUM severity with a base score of 6.7 according to the Common Vulnerability Scoring System (CVSS) v3.1. The attack complexity is considered LOW, but the confidentiality, integrity, and availability impacts are all rated as HIGH.

Technical Details of CVE-2021-34721

The following technical details provide insight into the vulnerability and its implications:

Vulnerability Description

The vulnerability allows an authenticated, local attacker to escalate privileges on an affected device, gaining root access through the CLI of Cisco IOS XR Software.

Affected Systems and Versions

The affected product is Cisco IOS XR Software, and all versions are susceptible to this vulnerability.

Exploitation Mechanism

An attacker needs to be authenticated locally to exploit this vulnerability, gaining root access via the CLI and executing malicious commands.

Mitigation and Prevention

To address CVE-2021-34721, consider the following mitigation strategies:

Immediate Steps to Take

Monitor and restrict access to sensitive devices and the CLI interface.
Apply vendor-supplied patches promptly once they are available.

Long-Term Security Practices

Implement the principle of least privilege to restrict unauthorized users from executing commands with elevated privileges.
Regularly update and patch the software to mitigate known vulnerabilities.

Patching and Updates

Stay informed about security advisories from Cisco and apply patches or updates as recommended to secure your systems against CVE-2021-34721.