CVE-2025-9079
📋 TL;DR
This vulnerability allows admin users in Mattermost to execute arbitrary code by uploading malicious plugins to the prepackaged plugins directory. The system fails to validate import directory path configuration, enabling remote code execution. All Mattermost instances running affected versions with admin users are at risk.
💻 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
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise with attacker gaining full control of the Mattermost server, potentially leading to data theft, lateral movement, or ransomware deployment.
Likely Case
Admin user or compromised admin account uploads malicious plugin leading to server compromise, data exfiltration, or persistence mechanisms.
If Mitigated
Limited impact with proper admin account controls, plugin validation, and network segmentation in place.
🎯 Exploit Status
Exploitation requires admin credentials but is straightforward once access is obtained.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Update to Mattermost 10.8.4, 10.5.9, 9.11.18, 10.10.2, or 10.9.4
Vendor Advisory: https://mattermost.com/security-updates
Restart Required: Yes
Instructions:
1. Backup your Mattermost configuration and database. 2. Download the patched version from Mattermost releases. 3. Stop the Mattermost service. 4. Replace the installation with the patched version. 5. Restart the Mattermost service. 6. Verify the version is updated.
🔧 Temporary Workarounds
Disable plugin uploads
allTemporarily disable plugin upload functionality for all users
Edit config.json: set "EnableUploads" to false
Restart Mattermost service
Restrict admin privileges
allReduce number of admin users and implement MFA for admin accounts
🧯 If You Can't Patch
- Implement strict admin account controls with multi-factor authentication
- Network segment Mattermost server and monitor for unusual plugin upload activity
🔍 How to Verify
Check if Vulnerable:
Check Mattermost version via System Console > About or run: mattermost versionCheck Version:
mattermost versionVerify Fix Applied:
Confirm version is updated to 10.8.4, 10.5.9, 9.11.18, 10.10.2, or 10.9.4📡 Detection & Monitoring
Log Indicators:
- Unusual plugin uploads from admin accounts
- Plugin installation events outside maintenance windows
- Errors in plugin validation logs
Network Indicators:
- Unexpected outbound connections from Mattermost server
- Unusual file transfers from Mattermost instance
SIEM Query:
source="mattermost" AND (event="plugin_upload" OR event="plugin_install")