CVE-2021-37859 : Exploit Details and Defense Strategies

This article provides details about CVE-2021-37859, a reflected cross-site scripting vulnerability affecting Mattermost OAuth-enabled instances.

Understanding CVE-2021-37859

CVE-2021-37859 is a vulnerability that allows attackers to bypass security measures in OAuth-enabled instances of Mattermost, potentially leading to cross-site scripting attacks.

What is CVE-2021-37859?

CVE-2021-37859 is a reflected cross-site scripting vulnerability that affects specific versions of Mattermost, allowing attackers to execute malicious scripts in the context of a user's session.

The Impact of CVE-2021-37859

This vulnerability poses a high risk, with a base score of 7.1 (High) according to the CVSS v3.1 metrics. Attackers can exploit this flaw to compromise the confidentiality and integrity of affected systems.

Technical Details of CVE-2021-37859

CVE-2021-37859 is classified as a CWE-79 - Cross-site Scripting (XSS) vulnerability. The affected versions of Mattermost include custom version 5.32.0.

Vulnerability Description

The vulnerability allows for a bypass in the OAuth flow, leading to a reflected cross-site scripting attack in Mattermost instances configured with OAuth.

Affected Systems and Versions

The vulnerability affects Mattermost version 5.32.0 specifically, while versions 5.34.5 and 5.35.4 are unaffected.

Exploitation Mechanism

Attackers can exploit this vulnerability by crafting malicious URLs that inject and execute scripts within the context of the targeted user's browser session.

Mitigation and Prevention

To mitigate the risks associated with CVE-2021-37859, immediate action should be taken to apply necessary security measures and patches.

Immediate Steps to Take

Users are advised to update their Mattermost instances to unaffected versions (5.34.5 and 5.35.4) or apply patches provided by the vendor to address the vulnerability.

Long-Term Security Practices

In addition to immediate patching, users should implement a robust security posture, including regular security updates and monitoring of potentially vulnerable components.

Patching and Updates

Regularly check for security updates from Mattermost and apply them promptly to ensure protection against known vulnerabilities.