CVE-2024-23488 in Mattermost
Summary
by MITRE • 02/29/2024
Mattermost fails to properly restrict the access of files attached to posts in an archived channel, resulting in members being able to access files of archived channels even if the “Allow users to view archived channels” option is disabled.
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Analysis
by VulDB Data Team • 05/12/2025
The vulnerability identified as CVE-2024-23488 represents a critical access control flaw within the Mattermost collaboration platform that undermines the security boundaries established for archived channels. This issue specifically affects the file access controls mechanism where the platform fails to properly enforce restrictions on attachments posted within archived channels, creating a scenario where unauthorized users can bypass intended security measures.
The technical flaw manifests in the platform's inability to correctly validate user permissions when accessing files from archived channels, regardless of the administrative setting that should disable access to such content. When the "Allow users to view archived channels" option is disabled, the system should prevent any access to channel content including file attachments, yet this vulnerability allows members to retrieve and view files that were posted in archived channels. This represents a direct violation of the principle of least privilege and demonstrates a failure in the access control validation logic.
From an operational impact perspective, this vulnerability creates significant security risks for organizations relying on Mattermost for sensitive communications and document sharing. Attackers or unauthorized users who gain access to archived channel files can potentially access confidential information, intellectual property, or sensitive business documents that were intended to be restricted. The vulnerability is particularly concerning because it operates silently without explicit user notification, making it difficult to detect unauthorized access attempts and potentially leading to data leakage incidents that could result in regulatory compliance violations and reputational damage.
The security implications of this vulnerability align with CWE-284, which addresses improper access control, and can be mapped to ATT&CK technique T1078.004 related to valid accounts and T1566.001 related to spearphishing via email, as unauthorized access to archived channel files could facilitate further exploitation. Organizations using Mattermost should immediately implement mitigations including disabling the archived channel access feature until the vulnerability is patched, reviewing existing access controls, and monitoring for unauthorized file access patterns. Additionally, administrators should consider implementing additional access logging and alerting mechanisms to detect potential exploitation attempts and ensure compliance with data protection regulations such as GDPR and HIPAA that may govern the handling of sensitive information within collaborative platforms.
The vulnerability demonstrates a fundamental breakdown in the platform's security architecture where the administrative controls designed to protect sensitive information are bypassed through a flaw in the access validation process. This type of issue commonly arises from insufficient input validation and inadequate permission checking mechanisms within collaborative software platforms, where the complexity of managing user access across different channel states creates opportunities for security gaps. Organizations should conduct immediate security assessments of their Mattermost deployments to identify affected systems and implement temporary workarounds while permanent patches are deployed to address the underlying access control implementation.