CVE-2018-21260 in Mattermost Server
Summary
by MITRE
An issue was discovered in Mattermost Server before 4.8.1, 4.7.4, and 4.6.3. WebSocket events were accidentally sent during certain user-management operations, violating user privacy.
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Analysis
by VulDB Data Team • 10/25/2020
The vulnerability identified as CVE-2018-21260 represents a significant privacy breach in the Mattermost collaborative platform where unauthorized WebSocket event transmission occurred during user management operations. This issue affected versions prior to 4.8.1, 4.7.4, and 4.6.3, exposing sensitive user data through unintended communication channels that should have remained private. The flaw emerged from improper handling of WebSocket connections during administrative user management tasks, creating an avenue for unauthorized information disclosure.
WebSocket technology in Mattermost enables real-time communication between server and clients, facilitating instant messaging and notifications. However, this vulnerability occurred when the system failed to properly isolate WebSocket events during user management operations, allowing sensitive information about user activities, status changes, and administrative actions to be transmitted to unauthorized parties. The technical implementation flaw involved inadequate access control mechanisms during these specific operations, where the system continued to broadcast events that should have been restricted to authorized participants only.
The operational impact of this vulnerability extends beyond simple privacy concerns to encompass potential security risks for organizations relying on Mattermost for communication. When user management operations such as creating, modifying, or deleting user accounts trigger WebSocket events, the unintended transmission of this information could expose sensitive details including user presence status, account modifications, and administrative actions to unauthorized users. This breach violates fundamental security principles of least privilege and data separation, as described in the CWE-284 access control weakness classification. The vulnerability creates opportunities for attackers to gather intelligence about user activities and system administration patterns, potentially enabling more sophisticated attacks.
Organizations using affected Mattermost versions faced significant risk of unauthorized information disclosure during routine administrative tasks. The vulnerability could be exploited by malicious actors who gained access to the platform, allowing them to monitor user management activities and potentially correlate this information with other security events. This exposure aligns with ATT&CK technique T1082 for system information discovery, as attackers could use the leaked WebSocket events to gather information about system users and administrative activities. The security implications extend to potential insider threat scenarios where unauthorized users could monitor legitimate administrative operations, undermining trust in the platform's privacy controls.
The recommended mitigation strategy involves upgrading to Mattermost versions 4.8.1, 4.7.4, or 4.6.3, which contain patches addressing the improper WebSocket event handling during user management operations. Organizations should also implement additional monitoring of WebSocket traffic to detect anomalous event transmission patterns, ensuring that only authorized users receive relevant notifications during administrative tasks. Security teams should review their access control policies and verify that WebSocket event broadcasting is properly restricted during sensitive operations. The fix typically involves implementing stricter access controls and ensuring that WebSocket events are properly filtered based on user permissions and operational context, preventing the accidental exposure of sensitive information that should remain private during user management activities.