CVE-2024-32939
📋 TL;DR
This vulnerability in Mattermost exposes remote users' email addresses when shared channels are enabled, even when email visibility is otherwise restricted. It affects organizations using Mattermost with shared channels functionality. The issue allows unauthorized disclosure of sensitive user information.
💻 Affected Systems
- Mattermost
📦 What is this software?
Mattermost by Mattermost
Mattermost by Mattermost
Mattermost by Mattermost
Mattermost by Mattermost
⚠️ Risk & Real-World Impact
Worst Case
Attackers could harvest email addresses of remote users across federated Mattermost instances, enabling targeted phishing campaigns or identity correlation attacks.
Likely Case
Internal users with access to shared channels could view email addresses of remote users that should be hidden, violating privacy expectations.
If Mitigated
With proper access controls and monitoring, impact is limited to information disclosure without system compromise.
🎯 Exploit Status
Exploitation requires access to Mattermost instance with shared channels enabled.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 9.9.2, 9.5.8, 9.10.1, 9.8.3
Vendor Advisory: https://mattermost.com/security-updates
Restart Required: Yes
Instructions:
1. Backup your Mattermost instance. 2. Download and install the patched version from Mattermost releases. 3. Restart the Mattermost service. 4. Verify the update was successful.
🔧 Temporary Workarounds
Disable Shared Channels
allTemporarily disable shared channels feature to prevent exposure of email addresses.
mmctl config set ServiceSettings.EnableSharedChannels false
🧯 If You Can't Patch
- Disable shared channels feature immediately
- Implement strict access controls and monitor user activity logs
🔍 How to Verify
Check if Vulnerable:
Check Mattermost version and verify if shared channels are enabled in System Console > Environment > Shared Channels.Check Version:
mmctl versionVerify Fix Applied:
Verify version is updated to patched version and test that remote user email addresses are properly redacted.📡 Detection & Monitoring
Log Indicators:
- Unusual access patterns to user profile data
- Multiple queries for remote user information
Network Indicators:
- Increased API calls to user endpoints from shared channel participants
SIEM Query:
source="mattermost" AND (event="user_viewed" OR event="profile_viewed") AND remote_user=true