CVE-2021-40344 : Exploit Details and Defense Strategies

Nagios XI 5.8.5 has a vulnerability that allows for remote command execution through the upload of a crafted PHP script.

Understanding CVE-2021-40344

This CVE involves an issue in the Custom Includes section of the Nagios XI Admin panel that permits the upload of files with arbitrary extensions under certain conditions.

What is CVE-2021-40344?

Vulnerability Type: Remote Command Execution
CVE ID: CVE-2021-40344
CVE Published Date: October 26, 2021

The vulnerability allows administrators to upload PHP scripts by exploiting MIME type restrictions.

The Impact of CVE-2021-40344

The presence of this vulnerability can lead to remote command execution on the affected Nagios XI system.

Technical Details of CVE-2021-40344

This section delves into the specific technical aspects of the CVE.

Vulnerability Description

An administrator can upload files with arbitrary extensions if the MIME type corresponds to an image.
This allows for the upload of a crafted PHP script, enabling remote command execution.

Affected Systems and Versions

Product: Nagios XI
Versions: 5.8.5
Status: Affected

Exploitation Mechanism

Uploading files with specific extensions under the guise of image files due to MIME type validation loopholes.

Mitigation and Prevention

Mitigation strategies to address and prevent exploitation of the CVE.

Immediate Steps to Take

Disable file uploads in the Custom Includes section as a temporary measure.
Implement firewall rules to restrict access to vulnerable sections.
Regularly monitor the system for unauthorized changes.

Long-Term Security Practices

Enforce a strict file upload policy with stringent extension and MIME type validations.
Conduct regular security assessments and audits to identify and remediate vulnerabilities.

Patching and Updates

Apply the necessary patches provided by Nagios to eliminate the vulnerability.
Stay informed about security advisories and updates from the vendor to ensure timely protection.