CVE-2023-3582 in Server
Summary
by MITRE • 07/17/2023
Mattermost fails to verify channel membership when linking a board to a channel allowing a low-privileged authenticated user to link a Board to a private channel they don't have access to,
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Analysis
by VulDB Data Team • 07/17/2023
The vulnerability identified as CVE-2023-3582 represents a critical access control flaw within the Mattermost collaboration platform that undermines the security model governing channel and board relationships. This issue specifically targets the permission validation mechanisms that should prevent unauthorized users from establishing connections between boards and channels, particularly private channels that require specific membership rights to access. The flaw exists in the board-channel linking functionality where the system fails to perform proper channel membership verification before allowing the association to be created. This represents a direct violation of the principle of least privilege and could enable malicious actors with lower privileges to gain unauthorized access to sensitive information contained within private channels through the board linking mechanism.
The technical implementation of this vulnerability stems from inadequate input validation and authorization checks within the board-channel relationship creation process. When a user attempts to link a board to a channel, the system should verify that the user possesses the necessary permissions to access the target channel before permitting the operation. However, the Mattermost platform lacks this crucial verification step, allowing any authenticated user to perform the linking operation regardless of their actual channel membership status. This oversight creates a pathway for privilege escalation where users can essentially bypass the normal channel access controls by creating board-channel associations that subsequently provide them with indirect access to private channel content through the board interface.
The operational impact of this vulnerability extends beyond simple unauthorized access, as it fundamentally compromises the integrity of Mattermost's permission architecture and could enable data exfiltration or information disclosure attacks. An attacker with low-privileged access could link a board to a private channel containing sensitive project information, configuration details, or confidential communications, effectively creating a backdoor access mechanism that circumvents normal security controls. This vulnerability is particularly concerning in enterprise environments where Mattermost serves as a primary collaboration platform for teams handling proprietary information, regulatory compliance data, or strategic business assets. The attack vector is relatively simple to exploit, requiring only basic authenticated access and knowledge of the board-channel linking functionality, making it accessible to a wide range of threat actors.
Organizations utilizing Mattermost should consider this vulnerability as a high-priority security concern that requires immediate attention through patch management and configuration hardening. The recommended mitigation strategy involves implementing proper channel membership verification before allowing board-channel associations to be created, ensuring that users cannot link boards to channels they do not have explicit access to. This aligns with the security principle of defense in depth and addresses the core issue identified in the Common Weakness Enumeration catalog under CWE-284 which deals with improper access control. Security teams should also implement monitoring for unusual board-channel linking activities and consider temporary workarounds such as restricting board creation privileges or disabling the board-channel linking functionality until the vulnerability is properly patched.
The broader implications of this vulnerability highlight the importance of comprehensive access control validation within collaborative platforms and the potential for seemingly minor functionality flaws to create significant security risks. This issue demonstrates how interconnected systems within modern collaboration platforms can create unexpected attack vectors when proper authorization checks are not implemented across all operational boundaries. The vulnerability also relates to techniques described in the MITRE ATT&CK framework under privilege escalation and lateral movement tactics, where attackers can leverage weak access controls to expand their operational capabilities within a compromised environment. Organizations should conduct thorough security assessments of their Mattermost deployments to identify similar access control gaps and ensure that all user interactions with sensitive data maintain proper authorization validation mechanisms.