CVE-2023-5331 in Mattermost
Summary
by MITRE • 10/25/2023
Mattermost fails to properly check the creator of an attached file when adding the file to a draft post, potentially exposing unauthorized file information.
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Analysis
by VulDB Data Team • 10/27/2023
The vulnerability identified as CVE-2023-5331 represents a critical access control flaw within the Mattermost collaboration platform that undermines the integrity of file sharing mechanisms. This issue specifically affects the file attachment functionality within draft posts, where the system fails to validate whether the authenticated user has proper authorization to access or reference files they are attempting to attach. The flaw exists in the file validation logic that governs how attachments are processed when users create draft messages, creating a potential vector for unauthorized information disclosure.
The technical implementation of this vulnerability stems from insufficient authorization checks during the file attachment process within Mattermost's draft post functionality. When users attempt to add files to draft messages, the system should verify that the requesting user has appropriate permissions to access the target file, particularly when that file was originally created by a different user. However, the current implementation bypasses this crucial validation step, allowing malicious actors to reference and potentially expose files they should not have access to. This represents a direct violation of the principle of least privilege and demonstrates a failure in the platform's access control mechanisms.
The operational impact of this vulnerability extends beyond simple information disclosure, potentially enabling broader security compromise within collaborative environments. An attacker with access to a Mattermost instance could exploit this weakness to gain unauthorized visibility into files created by other users, potentially accessing sensitive documents, proprietary information, or confidential communications. The vulnerability is particularly concerning in enterprise environments where Mattermost serves as a primary communication platform, as it could facilitate lateral movement and information gathering activities that align with tactics described in the attack pattern framework. This flaw directly relates to CWE-284, which addresses improper access control, and could be leveraged to achieve unauthorized access patterns consistent with ATT&CK technique T1078.
Mitigation strategies for CVE-2023-5331 should focus on implementing robust authorization checks within the file attachment pipeline, ensuring that all file references are validated against the user's permissions before being added to draft posts. Organizations should prioritize applying vendor-provided patches or updates that address the specific access control validation issue. Additionally, security teams should implement monitoring for unusual file attachment patterns within draft posts, as these could indicate exploitation attempts. The remediation process should include comprehensive testing of file sharing workflows to ensure that proper access controls are enforced throughout all stages of file handling, from creation through attachment and sharing. Regular security assessments of collaboration platforms should also include verification of access control mechanisms to prevent similar issues from emerging in other components of the system architecture.