CVE-2021-31356 Explained : Impact and Mitigation

A detailed analysis of a command injection vulnerability in command processing on Juniper Networks Junos OS Evolved, affecting various versions.

Understanding CVE-2021-31356

This CVE describes multiple shell-injection vulnerabilities in the EVO UI wrapper scripts of Junos OS Evolved.

What is CVE-2021-31356?

A command injection flaw in Juniper Networks Junos OS Evolved allows authenticated attackers to run arbitrary shell commands, bypassing command authorization restrictions.

The Impact of CVE-2021-31356

The vulnerability has a CVSS base score of 7.8, posing a high severity threat with high impacts on confidentiality, integrity, and availability.

Technical Details of CVE-2021-31356

This section provides specific technical details related to the vulnerability.

Vulnerability Description

The flaw permits attackers with CLI access to execute shell commands within the user's context, bypassing command authorization restrictions.

Affected Systems and Versions

Versions impacted include Junos OS Evolved 20.4R3-S1-EVO and all versions of 21.1-EVO and 21.2-EVO.

Exploitation Mechanism

The vulnerability allows attackers to bypass configured access protections and execute unauthorized shell commands.

Mitigation and Prevention

Details on how to mitigate the risks associated with CVE-2021-31356.

Immediate Steps to Take

Utilize access lists or firewall filters to restrict CLI access to trusted hosts and administrators.

Long-Term Security Practices

Ensure systems are regularly updated with the latest software releases to fix the vulnerability.

Patching and Updates

Juniper advises upgrading to Junos OS Evolved 20.4R3-S1-EVO, 21.3R1-EVO, or subsequent releases to address this issue.