CVE-2019-20841 in Mattermost Server
Summary
by MITRE
An issue was discovered in Mattermost Server before 5.18.0, 5.17.2, 5.16.4, 5.15.4, and 5.9.7. CSRF can sometimes occur via a crafted web site for account takeover attacks.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 10/25/2020
The vulnerability identified as CVE-2019-20841 represents a critical cross-site request forgery flaw within the Mattermost Server platform that affects multiple version branches including 5.18.0, 5.17.2, 5.16.4, 5.15.4, and 5.9.7. This vulnerability stems from inadequate protection mechanisms that fail to properly validate and authenticate requests originating from external domains, creating a pathway for malicious actors to execute unauthorized actions on behalf of legitimate users. The flaw specifically manifests when users visit a malicious website that contains crafted requests designed to exploit the server's insufficient cross-site request forgery protection measures.
The technical implementation of this vulnerability allows attackers to construct malicious web pages that can automatically submit requests to the Mattermost server without user consent or knowledge. This occurs because the server fails to properly verify the origin of requests, particularly when users are authenticated and their session cookies are present in the browser. The vulnerability operates through the manipulation of HTTP requests that appear legitimate to the server but are actually crafted by attackers to perform actions such as changing user passwords, modifying account settings, or executing administrative functions. This type of attack falls under the category of CWE-352 Cross-Site Request Forgery, which is classified as a common web application security weakness that has been consistently identified in security assessments and vulnerability scans.
The operational impact of CVE-2019-20841 is severe and potentially catastrophic for organizations relying on Mattermost for communication and collaboration. Successful exploitation could result in complete account takeover scenarios where attackers gain unauthorized access to user accounts, potentially leading to data breaches, unauthorized communications, and the ability to manipulate team configurations and access controls. The vulnerability is particularly dangerous because it can be exploited through social engineering tactics where users are unknowingly directed to malicious websites, making it difficult to detect and prevent. Organizations using Mattermost in environments where sensitive communications occur face significant risks, as attackers could potentially access confidential information shared within teams, modify critical configurations, or even escalate privileges to administrative levels.
Mitigation strategies for this vulnerability involve immediate patching of affected Mattermost server versions to the latest releases that contain proper CSRF protection mechanisms. The recommended approach includes upgrading to Mattermost Server version 5.18.0 or later, which implements robust anti-CSRF token validation and proper request origin verification. Security administrators should also implement additional protective measures such as configuring proper Content Security Policy headers, enabling additional authentication factors, and conducting regular security assessments to identify potential attack vectors. The mitigation aligns with ATT&CK technique T1566.001 for credential access through social engineering and T1078 for valid accounts usage, making it critical for organizations to address this vulnerability promptly. Organizations should also establish monitoring procedures to detect suspicious activities related to account modifications and implement user education programs to reduce the risk of successful social engineering attacks that leverage this vulnerability.