CVE-2019-20873 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. It allows attackers to obtain sensitive information during user activation/deactivation.
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Analysis
by VulDB Data Team • 10/25/2020
The vulnerability identified as CVE-2019-20873 represents a sensitive information disclosure flaw within the Mattermost server software ecosystem. This security weakness affects multiple versions of the Mattermost platform including the 5.9.0, 5.8.1, 5.7.3, and 4.10.8 releases, indicating a widespread impact across the software's version history. The vulnerability specifically manifests during user activation and deactivation processes, suggesting that the issue is tied to the server's user management functionality and authentication mechanisms. This type of information disclosure vulnerability falls under the category of CWE-200, which encompasses weaknesses that can lead to unauthorized information exposure. The affected system components likely include user account management modules, authentication services, and potentially session handling mechanisms that process user state transitions.
The technical nature of this vulnerability allows attackers to exploit the user activation and deactivation workflows to extract sensitive data that should remain protected. During these operations, the system may inadvertently expose user credentials, session tokens, personal identification information, or other confidential data that is typically restricted to authorized personnel. The flaw likely stems from insufficient input validation, improper access controls, or inadequate output sanitization within the user management code paths. Attackers could potentially leverage this vulnerability to gain insights into user accounts, authentication details, or system configurations that would normally be protected. The operational impact extends beyond simple information disclosure as it could enable further attacks such as credential harvesting, account takeover attempts, or social engineering campaigns based on the acquired sensitive data.
The implications of this vulnerability are particularly concerning given Mattermost's role as a secure communication platform for enterprise environments. Organizations relying on Mattermost for internal communications, collaboration, and secure messaging may face significant risks if attackers successfully exploit this flaw. The vulnerability could compromise the confidentiality of user accounts, potentially exposing sensitive corporate communications, personal information, or proprietary data. Security professionals should consider this issue in the context of the ATT&CK framework, specifically under the T1078 technique for Valid Accounts and T1566 for Phishing, as the leaked information could facilitate more sophisticated attacks. The vulnerability's presence in multiple version lines suggests that organizations may have been exposed for extended periods without proper detection or mitigation.
Organizations utilizing Mattermost server software should prioritize immediate remediation by upgrading to versions 5.9.0, 5.8.1, 5.7.3, or 4.10.8, depending on their current deployment. System administrators should conduct comprehensive security assessments of their Mattermost installations to identify potential exploitation attempts and monitor for unusual user activity patterns that might indicate successful exploitation. Additional mitigations include implementing network-level controls to restrict access to user management endpoints, deploying intrusion detection systems to monitor for suspicious authentication-related traffic, and establishing robust monitoring procedures for user activation and deactivation events. Security teams should also review access controls and permissions within their Mattermost environments to ensure that only authorized personnel can perform user management operations. The vulnerability highlights the importance of proper input validation and output sanitization in authentication and user management systems, emphasizing the need for comprehensive security testing throughout the software development lifecycle.