CVE-2023-5160 in Mattermost
Summary
by MITRE • 10/25/2023
Mattermost fails to check the Show Full Name option at the /api/v4/teams/TEAM_ID/top/team_members endpoint allowing a member to get the full name of another user even if the Show Full Name option was disabled
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Analysis
by VulDB Data Team • 10/25/2023
The vulnerability described in CVE-2023-5160 represents a critical authorization flaw within the Mattermost communication platform that directly violates fundamental security principles of user privacy and data protection. This issue affects the /api/v4/teams/TEAM_ID/top/team_members endpoint where the system fails to properly enforce the Show Full Name configuration setting that users can set within their profile preferences. The flaw exists at the application logic level where the platform does not validate whether the requesting user has sufficient permissions or whether the target user has explicitly disabled the visibility of their full name. This represents a clear violation of the principle of least privilege and demonstrates a failure in access control implementation that allows for unauthorized information disclosure.
The technical nature of this vulnerability stems from the absence of proper authorization checks within the API endpoint implementation. When a user accesses the team_members endpoint, the system should verify that the requesting user has appropriate permissions to view the full names of other users, particularly when those users have explicitly configured their profiles to hide this information. The flaw indicates that the application layer fails to cross-reference the user's privacy settings with the access control mechanisms, creating an information leakage scenario where sensitive user data becomes accessible through an API call that should respect user-defined privacy controls. This vulnerability specifically relates to CWE-668 - Exposure of Resource to Wrong Sphere and CWE-284 - Improper Access Control, both of which are fundamental categories in the CWE hierarchy that address improper privilege management and resource access control.
The operational impact of this vulnerability extends beyond simple privacy concerns to potentially enable more sophisticated attack vectors that could be leveraged in broader security compromise scenarios. An attacker with access to a valid session or API token could exploit this flaw to gather intelligence about users within a team, potentially mapping user relationships and identifying key personnel based on their full names. This information could be combined with other reconnaissance activities to facilitate social engineering attacks, account takeovers, or targeted phishing campaigns. The vulnerability also impacts the principle of defense in depth since it allows for bypassing the built-in privacy controls that users rely on to protect their personal information within the platform. From an attacker's perspective, this represents a low-effort, high-impact method for information gathering that could be automated and scaled across multiple team environments.
Mitigation strategies for this vulnerability should focus on implementing robust access control mechanisms that respect user privacy settings and enforce proper authorization checks at the API layer. Organizations should immediately implement code-level fixes that validate the Show Full Name setting before returning user information through the team_members endpoint. The solution requires ensuring that any API call attempting to retrieve user information respects the privacy preferences set by individual users, with appropriate logging and monitoring of access patterns to detect potential abuse. Security teams should also consider implementing rate limiting and anomaly detection mechanisms around this endpoint to prevent automated enumeration attacks. From a broader security perspective, this vulnerability highlights the importance of regularly auditing API endpoints for proper access control implementation and ensuring that user privacy controls are consistently enforced throughout the application. The remediation process should include comprehensive testing to verify that the fix properly enforces privacy settings and that no other similar access control bypasses exist within the platform. This vulnerability also underscores the need for adherence to security best practices such as those outlined in the OWASP API Security Top 10 and NIST SP 800-53 security controls, particularly those related to access control and information classification.