CVE-2025-24526
📋 TL;DR
This vulnerability allows authenticated Mattermost users to export archived channel contents even when the 'Allow users to view archived channels' setting is disabled. This violates intended access controls and could expose sensitive information from archived channels. Affected users are those running vulnerable Mattermost versions with archived channels containing sensitive data.
💻 Affected Systems
- Mattermost Team Edition
- Mattermost Enterprise Edition
📦 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
Unauthorized access to sensitive archived channel data including confidential communications, files, and proprietary information, potentially leading to data breaches or intellectual property theft.
Likely Case
Users with legitimate access to Mattermost but not to archived channels can export and view historical conversations they shouldn't have access to, violating data segregation policies.
If Mitigated
Limited impact if archived channels contain only non-sensitive information or if strict user access controls are already in place.
🎯 Exploit Status
Exploitation requires authenticated access to Mattermost and knowledge of channel export functionality. No special privileges needed beyond standard user access.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Update to Mattermost 9.11.8, 10.1.4, 10.2.3, 10.3.3, or 10.4.2
Vendor Advisory: https://mattermost.com/security-updates
Restart Required: Yes
Instructions:
1. Backup your Mattermost database and configuration. 2. Download the patched version from mattermost.com/download. 3. Stop the Mattermost service. 4. Replace the existing installation with the patched version. 5. Restart the Mattermost service. 6. Verify the version is updated.
🔧 Temporary Workarounds
Disable Channel Export Feature
allTemporarily disable the channel export functionality for all users until patching can be completed.
Update System Console > Site Configuration > Users and Teams > Enable Channel Export to false
Enable Archived Channel Viewing
allEnable the 'Allow users to view archived channels' setting to remove the access control bypass condition.
Update System Console > Site Configuration > Users and Teams > Allow users to view archived channels to true
🧯 If You Can't Patch
- Implement strict access controls and monitor user activity for unauthorized channel export attempts
- Archive sensitive channels to a separate system and delete them from Mattermost to remove exposure
🔍 How to Verify
Check if Vulnerable:
Check Mattermost version via System Console > About Mattermost. If version matches affected ranges and you have archived channels with 'Allow users to view archived channels' disabled, you are vulnerable.Check Version:
From Mattermost CLI: mattermost version or check System Console > About MattermostVerify Fix Applied:
After patching, verify version is updated to patched version and test that users cannot export archived channels when the setting is disabled.📡 Detection & Monitoring
Log Indicators:
- Channel export activity for archived channels
- User accessing archived channels via export functionality
Network Indicators:
- HTTP POST requests to /api/v4/channels/{channel_id}/export endpoint for archived channels
SIEM Query:
source="mattermost" AND ("channel export" OR "exported channel") AND channel_status="archived"