CVE-2025-4981
📋 TL;DR
This vulnerability allows authenticated Mattermost users to write files to arbitrary locations on the filesystem by uploading archives containing path traversal sequences in filenames. This can lead to remote code execution when file uploads and document search by content are enabled. All Mattermost instances running affected versions with default configurations are vulnerable.
💻 Affected Systems
- Mattermost
📦 What is this software?
Mattermost Server by Mattermost
Mattermost Server by Mattermost
Mattermost Server by Mattermost
Mattermost Server by Mattermost
Mattermost Server by Mattermost
Mattermost Server by Mattermost
Mattermost Server by Mattermost
Mattermost Server by Mattermost
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete system compromise, data exfiltration, or ransomware deployment.
Likely Case
Unauthorized file writes to sensitive locations, potential privilege escalation, and data manipulation.
If Mitigated
Limited impact if proper access controls and monitoring are in place, though file system integrity may still be compromised.
🎯 Exploit Status
Exploitation requires authenticated user access and specific configuration settings enabled
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 10.5.6, 9.11.16, 10.8.1, 10.7.3, 10.6.6 or later
Vendor Advisory: https://mattermost.com/security-updates
Restart Required: Yes
Instructions:
1. Backup your Mattermost instance. 2. Download the patched version from Mattermost downloads page. 3. Stop Mattermost service. 4. Replace with patched version. 5. Restart Mattermost service. 6. Verify version update.
🔧 Temporary Workarounds
Disable file content extraction
allDisable the ExtractContent setting to prevent archive extraction
Update config.json: "ExtractContent": false
Disable file attachments
allCompletely disable file attachments to prevent archive uploads
Update config.json: "EnableFileAttachments": false
🧯 If You Can't Patch
- Implement strict file upload restrictions and monitoring
- Apply network segmentation and limit Mattermost server access
🔍 How to Verify
Check if Vulnerable:
Check Mattermost version and verify FileSettings.EnableFileAttachments and FileSettings.ExtractContent are both trueCheck Version:
mattermost versionVerify Fix Applied:
Verify Mattermost version is patched (10.5.6+, 9.11.16+, 10.8.1+, 10.7.3+, or 10.6.6+)📡 Detection & Monitoring
Log Indicators:
- Unusual archive uploads, file write attempts to unexpected locations, path traversal patterns in filenames
Network Indicators:
- Large or unusual file uploads to Mattermost
SIEM Query:
source="mattermost" AND ("archive" OR "upload" OR "extract") AND (".." OR "../" OR "path traversal")