CVE-2017-18914 : Exploit Details and Defense Strategies

A problem was found in versions before 3.8.2, 3.7.5, and 3.6.7 of Mattermost Server where an external link may appear on an error page, even if not included in an allowlist.

Understanding CVE-2017-18914

This CVE identifies an issue in Mattermost Server versions prior to 3.8.2, 3.7.5, and 3.6.7, allowing external links to display on error pages without being on an allowlist.

What is CVE-2017-18914?

This CVE describes a vulnerability in Mattermost Server that could lead to the display of external links on error pages, bypassing the allowlist mechanism.

The Impact of CVE-2017-18914

The vulnerability could potentially expose users to malicious external links, impacting the security and integrity of the system.

Technical Details of CVE-2017-18914

Vulnerability Description

An external link can be shown on an error page in Mattermost Server versions before 3.8.2, 3.7.5, and 3.6.7, regardless of being on an allowlist.

Affected Systems and Versions

Mattermost Server versions before 3.8.2
Mattermost Server versions before 3.7.5
Mattermost Server versions before 3.6.7

Exploitation Mechanism

The vulnerability allows an external link to be displayed on error pages, potentially leading to users interacting with malicious content.

Mitigation and Prevention

Immediate Steps to Take

Upgrade Mattermost Server to version 3.8.2, 3.7.5, or 3.6.7 to mitigate the vulnerability.
Regularly monitor error pages for any unauthorized external links.

Long-Term Security Practices

Implement strict allowlisting mechanisms to control external links displayed on error pages.
Conduct regular security audits to identify and address any similar vulnerabilities.

Patching and Updates

Ensure timely installation of security patches and updates provided by Mattermost to address known vulnerabilities.