CVE-2019-20878 in Mattermost Server
Summary
by MITRE
An issue was discovered in Mattermost Server before 5.9.0, 5.8.1, 5.7.3, and 4.10.8. Changes, within the application, to e-mail addresses are mishandled.
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Analysis
by VulDB Data Team • 10/25/2020
The vulnerability identified as CVE-2019-20878 represents a critical flaw in the Mattermost Server authentication and user management system that affects multiple version lines including 4.10.8, 5.7.3, 5.8.1, and versions prior to 5.9.0. This issue stems from improper handling of email address modifications within the application's user management framework, creating potential security risks that could be exploited by malicious actors. The flaw specifically manifests when users attempt to update their email addresses within the system, indicating a fundamental weakness in the input validation and processing mechanisms that govern user account modifications.
The technical nature of this vulnerability falls under the category of improper input validation and authentication bypass risks, which aligns with CWE-20 (Improper Input Validation) and CWE-287 (Improper Authentication). The flaw occurs during the email address change process where the application fails to properly validate or sanitize the new email address before applying the modification. This misconfiguration allows for potential injection attacks or unauthorized modifications to user accounts, as the system does not adequately verify the legitimacy of the email address being submitted. Attackers could exploit this weakness to manipulate user account information, potentially gaining unauthorized access to other users' accounts or creating confusion within the authentication system.
The operational impact of CVE-2019-20878 extends beyond simple account modification issues, as it could enable attackers to perform account takeover attempts or facilitate social engineering attacks. When email addresses are improperly handled during updates, it creates opportunities for attackers to redirect notifications, manipulate account recovery processes, or establish persistent access to compromised accounts. The vulnerability affects the core authentication and authorization mechanisms of Mattermost, which is a critical collaboration platform used by organizations for secure communication. This weakness could allow unauthorized individuals to assume the identity of legitimate users, potentially accessing sensitive information, modifying system configurations, or disrupting collaborative workflows.
Organizations utilizing Mattermost Server versions affected by this vulnerability should prioritize immediate remediation through patch updates to versions 5.9.0, 5.8.1, 5.7.3, or 4.10.8 as appropriate. The mitigation strategy should include comprehensive security audits of user management processes, implementation of additional email validation mechanisms, and monitoring for unauthorized account modifications. Security teams should also consider implementing multi-factor authentication for critical user accounts and establishing automated alerts for email address changes to detect potential exploitation attempts. The vulnerability demonstrates the importance of robust input validation in authentication systems and aligns with ATT&CK technique T1078 (Valid Accounts) and T1566 (Phishing) as attackers could leverage this weakness to establish persistent access or facilitate targeted attacks against users within the organization.