CVE-2019-20862 in Mattermost Server
Summary
by MITRE
An issue was discovered in Mattermost Server before 5.13.0. Non-members may fetch a team's slash commands.
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Analysis
by VulDB Data Team • 10/25/2020
The vulnerability identified as CVE-2019-20862 represents a critical access control flaw within the Mattermost Server platform that existed prior to version 5.13.0. This issue fundamentally undermines the security model of the collaboration platform by allowing unauthorized users to access sensitive operational data. The flaw specifically affects the slash command functionality within team environments, creating a pathway for non-members to obtain information that should remain restricted to authenticated team members only. Mattermost is widely deployed across enterprise environments for secure communication and collaboration, making this vulnerability particularly concerning for organizations relying on its access controls to maintain data integrity and confidentiality.
The technical implementation of this vulnerability stems from insufficient authorization checks within the server's command handling mechanisms. When non-members attempt to access team-specific slash commands, the system fails to properly validate their membership status before returning the requested information. This misconfiguration creates a privilege escalation scenario where external parties can gather intelligence about team operations, command structures, and potentially sensitive operational details. The flaw operates at the application layer and demonstrates a failure in the principle of least privilege, where users should only have access to resources commensurate with their role and authentication status. This type of vulnerability is classified under CWE-284 which specifically addresses improper access control issues in software systems.
The operational impact of this vulnerability extends beyond simple information disclosure to potentially enable more sophisticated attacks within the Mattermost ecosystem. An attacker exploiting this flaw could map out team structures, identify active commands, and potentially discover patterns in team communication that might aid in social engineering or targeted attacks. The vulnerability affects the core functionality of team-based communication, where access control is fundamental to maintaining secure collaboration environments. Organizations using Mattermost for sensitive communications or compliance-sensitive operations would face significant risk exposure, as the disclosure of slash commands could reveal operational procedures and system configurations that might be leveraged in subsequent attacks. This vulnerability directly impacts the integrity and confidentiality aspects of the CIA triad, potentially exposing the system to further exploitation through reconnaissance activities.
Mitigation strategies for this vulnerability require immediate patching of Mattermost Server installations to version 5.13.0 or later, where the access control mechanisms have been properly implemented. Organizations should conduct thorough security assessments of their Mattermost deployments to identify any other potential access control gaps that might exist within their collaborative environments. Network segmentation and monitoring of unusual access patterns related to slash command queries should be implemented to detect potential exploitation attempts. The remediation process should include reviewing and validating all access control configurations within the platform, ensuring that proper authentication and authorization checks are enforced for all operations. Additionally, security teams should implement logging and alerting mechanisms specifically designed to detect unauthorized access attempts to team-specific resources, as this vulnerability could serve as a reconnaissance tool for attackers planning more extensive penetration attempts. The fix addresses the underlying CWE-284 issue by implementing proper access control validation that ensures only authenticated team members can access team-specific slash commands, thereby restoring the intended security boundaries within the Mattermost platform.