CVE-2024-1952 in Mattermost
Summary
by MITRE • 02/29/2024
Mattermost version 8.1.x before 8.1.9 fails to sanitize data associated with permalinks when a plugin updates an ephemeral post, allowing an authenticated attacker who can control the ephemeral post update to access individual posts' contents in channels they are not a member of.
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Analysis
by VulDB Data Team • 12/13/2024
The vulnerability identified as CVE-2024-1952 affects Mattermost versions 8.1.x prior to 8.1.9 and represents a critical access control flaw that undermines the platform's security model. This issue stems from inadequate data sanitization mechanisms within the permalink handling system when plugins interact with ephemeral posts, creating a pathway for authenticated attackers to bypass channel membership restrictions and access confidential content.
The technical flaw manifests in the improper sanitization of permalink data during plugin operations that modify ephemeral posts. When an authenticated user with appropriate permissions executes a plugin function that updates an ephemeral post, the system fails to properly validate or sanitize the permalink references associated with that operation. This vulnerability specifically impacts the authorization checks that should prevent users from accessing content in channels they do not belong to, creating a scenario where attackers can leverage legitimate plugin functionality to gain unauthorized access to restricted posts.
The operational impact of this vulnerability is significant as it allows attackers to exploit legitimate system features to access confidential communications and data that should remain restricted to authorized channel members. An authenticated attacker who can control the parameters of an ephemeral post update can potentially retrieve the contents of individual posts from channels where they lack membership privileges. This breach of information confidentiality undermines the fundamental security principles of channel-based access control that Mattermost implements to protect sensitive organizational communications.
This vulnerability aligns with CWE-200, which addresses improper information exposure, and represents a clear violation of the principle of least privilege that should govern all access control mechanisms. The flaw also intersects with ATT&CK technique T1078.004, which covers valid accounts used for lateral movement, as it allows attackers to leverage legitimate authenticated sessions to access unauthorized resources. The issue demonstrates how plugin systems can introduce security gaps when proper input validation and sanitization are not implemented across all data flows.
Organizations should immediately implement the patch for Mattermost version 8.1.9 or higher to remediate this vulnerability. Additionally, administrators should review plugin configurations and limit plugin access to only essential functions. Network monitoring should be enhanced to detect unusual patterns in ephemeral post updates and permalink access attempts. Regular security audits of plugin implementations are essential to identify similar sanitization gaps in other system components. The fix addresses the root cause by implementing proper data sanitization and authorization checks that validate user permissions before allowing access to permalink references, ensuring that channel membership restrictions remain intact even during plugin operations.