CVE-2025-41410
📋 TL;DR
This vulnerability allows attackers to create verified user accounts with arbitrary email domains during Slack imports in Mattermost. Attackers can bypass email-based team access restrictions by providing malicious Slack import data. Affected organizations are those running vulnerable Mattermost versions with Slack import functionality enabled.
💻 Affected Systems
- Mattermost
📦 What is this software?
Mattermost Server by Mattermost
Mattermost Server by Mattermost
Mattermost Server by Mattermost
⚠️ Risk & Real-World Impact
Worst Case
Unauthorized users gain access to restricted teams and channels, potentially accessing sensitive internal communications and data.
Likely Case
Attackers create accounts with spoofed email domains to join teams with email-based access controls, enabling information gathering and potential privilege escalation.
If Mitigated
With proper monitoring and access controls, unauthorized accounts are quickly detected and removed before causing significant damage.
🎯 Exploit Status
Requires ability to initiate Slack import with malicious data. May require some level of existing access or social engineering.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 10.10.3, 10.5.11, 10.11.3 or later
Vendor Advisory: https://mattermost.com/security-updates
Restart Required: No
Instructions:
1. Backup your Mattermost instance. 2. Upgrade to patched version (10.10.3, 10.5.11, or 10.11.3+). 3. Verify the upgrade completed successfully. 4. Monitor for any import-related anomalies.
🔧 Temporary Workarounds
Disable Slack Imports
allTemporarily disable Slack import functionality to prevent exploitation
Set 'EnableSlackImport' to 'false' in config.json
Restrict Import Permissions
allLimit who can perform Slack imports to trusted administrators only
Configure System Console > Users and Teams > Import to restrict permissions
🧯 If You Can't Patch
- Disable Slack import functionality entirely
- Implement strict monitoring of user account creation and import activities
🔍 How to Verify
Check if Vulnerable:
Check Mattermost version via System Console > About Mattermost. If version matches affected range and Slack imports are enabled, you are vulnerable.Check Version:
From Mattermost CLI: mattermost versionVerify Fix Applied:
After patching, verify version is 10.10.3+, 10.5.11+, or 10.11.3+. Test Slack import with non-matching email domains to ensure validation works.📡 Detection & Monitoring
Log Indicators:
- Unexpected user account creations during Slack imports
- User accounts with email domains not matching organization's domain
- Multiple import attempts from same source
Network Indicators:
- Unusual import traffic patterns
- Import requests with modified email data
SIEM Query:
source="mattermost" AND (event="user_created" OR event="import_completed") AND email NOT LIKE "%@yourdomain.com"