CVE-2025-4981 in Mattermost
Summary
by MITRE • 06/20/2025
Mattermost versions 10.5.x <= 10.5.5, 9.11.x <= 9.11.15, 10.8.x <= 10.8.0, 10.7.x <= 10.7.2, 10.6.x <= 10.6.5 fail to sanitize filenames in the archive extractor which allows authenticated users to write files to arbitrary locations on the filesystem via uploading archives with path traversal sequences in filenames, potentially leading to remote code execution. The vulnerability impacts instances where file uploads and document search by content is enabled (FileSettings.EnableFileAttachments = true and FileSettings.ExtractContent = true). These configuration settings are enabled by default.
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Analysis
by VulDB Data Team • 06/24/2025
The vulnerability described in CVE-2025-4981 represents a critical path traversal flaw within the Mattermost collaboration platform that affects multiple version streams including 10.5.x through 10.5.5, 9.11.x through 9.11.15, 10.8.x through 10.8.0, 10.7.x through 10.7.2, and 10.6.x through 10.6.5. This security weakness stems from inadequate sanitization of filenames during archive extraction processes, creating a significant attack vector for authenticated users who can exploit this flaw to write files to arbitrary locations on the target filesystem. The vulnerability operates through the manipulation of archive file contents where malicious actors can embed path traversal sequences within filenames, effectively bypassing normal file system access controls and permissions. The flaw specifically impacts systems where both file attachments and document search by content features are enabled, with these settings configured as default parameters in the Mattermost configuration, making the vulnerability particularly widespread across deployed instances.
The technical implementation of this vulnerability aligns with CWE-22, which describes path traversal or directory traversal vulnerabilities that occur when input data contains path elements that reference files or directories outside of the intended scope. Attackers can leverage this weakness by crafting archive files containing specially formatted filenames that include sequences such as ../ or ..\ that traverse directory structures. When Mattermost processes these archives for content extraction, the unsanitized filenames are directly used in file system operations, allowing attackers to write malicious files to critical system locations including configuration directories, binary execution paths, or other sensitive areas. The default enablement of both FileSettings.EnableFileAttachments = true and FileSettings.ExtractContent = true means that the attack surface is extensive, as these features are active on virtually all Mattermost deployments without additional configuration changes. This configuration default creates a dangerous scenario where authenticated users can potentially escalate privileges and achieve remote code execution by placing malicious payloads in strategic locations within the file system.
The operational impact of CVE-2025-4981 extends beyond simple unauthorized file writing, as it can lead to complete system compromise and remote code execution capabilities. An attacker who successfully exploits this vulnerability can place malicious binaries, scripts, or configuration files in locations where the Mattermost service has execution privileges, potentially allowing for persistent backdoor access or privilege escalation. The attack requires only authenticated access to the Mattermost platform, which can be achieved through legitimate user accounts or compromised credentials, making the vulnerability particularly dangerous in environments where user access controls are not properly enforced. This weakness can facilitate various attack patterns from the ATT&CK framework including privilege escalation through file system manipulation, persistence mechanisms through the creation of malicious startup scripts, and potentially lateral movement within network environments where Mattermost is integrated with other systems. The vulnerability's impact is amplified by the fact that it operates at the file system level, bypassing application-level security controls and potentially allowing attackers to modify core application components or system files.
Mitigation strategies for CVE-2025-4981 should prioritize immediate patching of affected Mattermost versions to the latest stable releases that contain the necessary sanitization fixes for filename handling during archive extraction. Organizations should also consider implementing additional protective measures including disabling the problematic features when not strictly required, specifically setting FileSettings.EnableFileAttachments = false and FileSettings.ExtractContent = false if these functionalities are not essential for business operations. Network segmentation and access controls should be enforced to limit user access to the Mattermost platform, reducing the attack surface for authenticated users who could potentially exploit this vulnerability. Security monitoring should be enhanced to detect unusual file system activity patterns, particularly around the creation of files in system directories or unexpected archive extraction operations. Organizations should also implement regular security assessments including vulnerability scanning and penetration testing to identify and remediate similar path traversal vulnerabilities in other applications and systems. The implementation of proper input validation and output encoding practices, combined with principle of least privilege access controls, will help prevent exploitation of similar vulnerabilities in the future and align with industry best practices for secure software development.