CVE-2024-42406
📋 TL;DR
This vulnerability allows attackers to bypass authorization controls in Mattermost when archived channel viewing is disabled. Attackers can retrieve post and file information from archived channels, including flagged/unread posts and files. Organizations running affected Mattermost versions with archived channel viewing disabled are impacted.
💻 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
⚠️ Risk & Real-World Impact
Worst Case
Sensitive archived channel content containing confidential information, intellectual property, or compliance data is exposed to unauthorized users, potentially leading to data breaches or regulatory violations.
Likely Case
Unauthorized users access archived channel content they shouldn't see, potentially exposing internal discussions, file attachments, or flagged content that should remain restricted.
If Mitigated
With proper access controls and monitoring, exposure is limited to low-sensitivity archived content, with minimal impact on operations or security posture.
🎯 Exploit Status
Requires authenticated user access but no special privileges beyond normal user account. Exploitation involves making specific API requests to access archived channel content.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 9.11.1, 9.10.2, 9.9.3, 9.5.9
Vendor Advisory: https://mattermost.com/security-updates
Restart Required: Yes
Instructions:
1. Backup Mattermost database and configuration. 2. Download appropriate patched version from Mattermost downloads. 3. Stop Mattermost service. 4. Install patched version following Mattermost upgrade guide. 5. Restart Mattermost service. 6. Verify version and functionality.
🔧 Temporary Workarounds
Enable archived channel viewing
allTemporarily enable the 'Enable users to view archived channels' setting to mitigate the authorization bypass until patching can be completed.
In System Console > Site Configuration > Users and Teams, set 'Enable users to view archived channels' to true
🧯 If You Can't Patch
- Enable archived channel viewing globally to remove the vulnerable condition
- Implement strict access controls and monitoring for archived channel access attempts
🔍 How to Verify
Check if Vulnerable:
Check Mattermost version via System Console > About Mattermost and verify if 'Enable users to view archived channels' is disabled in Site Configuration.Check Version:
In Mattermost System Console: navigate to About Mattermost sectionVerify Fix Applied:
After patching, verify version is updated to patched version and test that unauthorized users cannot access archived channel content when viewing is disabled.📡 Detection & Monitoring
Log Indicators:
- Unusual access patterns to archived channels
- API requests for archived channel content from unauthorized users
- Failed authorization attempts for archived content
Network Indicators:
- Increased API calls to channel endpoints with archived parameters
- Unusual data retrieval patterns from archived channels
SIEM Query:
source="mattermost" AND (event="channel_access" AND channel_status="archived") AND user_role!="admin"