CVE-2023-3586 in Server
Summary
by MITRE • 07/17/2023
Mattermost fails to disable public Boards after the "Enable Publicly-Shared Boards" configuration option is disabled, resulting in previously-shared public Boards to remain accessible.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 08/06/2023
The vulnerability identified as CVE-2023-3586 affects the Mattermost collaboration platform, specifically targeting its board sharing functionality within the application's configuration management system. This issue represents a critical access control flaw that undermines the security posture of organizations relying on Mattermost for team collaboration and document sharing. The vulnerability manifests when administrators disable the "Enable Publicly-Shared Boards" configuration option, yet the system fails to properly revoke access to boards that were previously shared publicly, creating a persistent security risk.
The technical root cause of this vulnerability lies in the improper implementation of access control mechanisms within Mattermost's board sharing subsystem. When the configuration option is disabled, the application should immediately invalidate all existing public board shares and revoke external access to previously shared content. However, the system maintains the public board references in its access control lists while removing the ability to create new public shares, leaving existing public boards accessible through their original sharing links. This represents a failure in the principle of least privilege and demonstrates inadequate session management for shared resources. The flaw can be categorized under CWE-668, which specifically addresses "Exposure of Resource to Wrong Sphere," where a resource is made available to entities that should not have access to it.
The operational impact of this vulnerability extends beyond simple data exposure to encompass broader security implications for organizations using Mattermost. Previously shared public boards may contain sensitive information, project plans, confidential discussions, or proprietary content that remains accessible to unauthorized parties even after administrators have explicitly disabled public sharing. This creates a persistent attack surface where malicious actors could potentially discover and access previously shared boards through direct links, particularly if the organization has not implemented additional access controls or monitoring. The vulnerability affects organizations of all sizes that rely on Mattermost's collaboration features, with potential consequences ranging from intellectual property exposure to regulatory compliance violations, especially in industries with strict data protection requirements such as healthcare, finance, or government sectors.
Organizations should implement immediate mitigations while awaiting official patches from Mattermost to address this vulnerability. The recommended approach includes disabling the public board sharing functionality at the application level and manually reviewing all existing public board shares to ensure they are properly secured or removed. Security teams should also implement monitoring solutions to detect unauthorized access attempts to board resources and establish procedures for regularly auditing shared content access. Additionally, organizations should consider implementing network-level controls to restrict access to Mattermost services and deploy web application firewalls that can detect and block suspicious access patterns to board resources. The vulnerability's characteristics align with tactics described in the attack pattern taxonomy under the MITRE ATT&CK framework, particularly in the privilege escalation and defense evasion categories, where attackers could leverage this flaw to maintain persistent access to sensitive information.