CVE-2021-31354 : Exploit Details and Defense Strategies

A vulnerability in Junos OS and Junos OS Evolved, specifically in the Juniper Agile License Client, could potentially lead to Remote Code Execution (RCE) if exploited. This vulnerability impacts systems configured in Network Mode, allowing attackers to cause Denial of Service (DoS) or RCE.

Understanding CVE-2021-31354

This section will provide insights into the impact, technical details, and mitigation strategies related to CVE-2021-31354.

What is CVE-2021-31354?

An Out Of Bounds (OOB) access vulnerability in the Juniper Agile License (JAL) Client in Junos OS and Junos OS Evolved, when configured in Network Mode, could be exploited by attackers to trigger a partial Denial of Service (DoS) or potential RCE. This vulnerability affects systems utilizing the Juniper Agile License Manager.

The Impact of CVE-2021-31354

The vulnerability in packet parsing logic on the affected client allows attackers with control over a JAL License Manager to potentially exploit the system by crafting malicious responses or spoofing a new JAL License Manager. Successful exploitation could result in a partial DoS or RCE. Only systems configured in Network Mode are susceptible to this issue.

Technical Details of CVE-2021-31354

This section explores the specifics of the vulnerability, including the description, affected systems, and exploitation mechanism.

Vulnerability Description

The vulnerability arises in the handling of responses by the JAL Client, impacting systems running Junos OS or Junos OS Evolved in Network Mode. Attackers can leverage this flaw for a DoS or RCE scenario.

Affected Systems and Versions

Juniper Networks Junos OS versions 19.2 to 21.1 and Junos OS Evolved versions 20.1R1-EVO to 21.2R2-EVO are susceptible to this vulnerability when configured in Network Mode.

Exploitation Mechanism

Exploiting this vulnerability requires an attacker to have control of a JAL License Manager or access to the local broadcast domain to craft malicious responses or spoof a new License Manager, leading to potential system compromise.

Mitigation and Prevention

Discover the immediate steps and long-term security practices to shield your systems from CVE-2021-31354.

Immediate Steps to Take

For immediate protection, consider disabling Network Mode and configuring the Junos License Client to operate in Standalone Mode.

Long-Term Security Practices

To fortify your systems against future vulnerabilities, ensure timely application of software updates and security patches provided by Juniper Networks.

Patching and Updates

Juniper Networks has released updated software versions to address CVE-2021-31354, including Junos OS 19.3R3-S3, 20.1R2-S2, 20.1R3-S1, 20.2R3-S2, 20.3R3, 20.4R3, 21.1R2, 21.2R1, and subsequent releases. Similarly, Junos OS Evolved 21.2R2-EVO, 21.3R1-EVO, and later versions contain the necessary fixes.