CVE-2025-3227
📋 TL;DR
This vulnerability allows authenticated Mattermost users without proper channel management permissions to add or remove users from public and private channels by manipulating playbook run participants. It affects Mattermost instances with playbooks enabled where runs are linked to channels. The impact is limited to authenticated users but bypasses intended permission controls.
💻 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
Mattermost Server by Mattermost
⚠️ Risk & Real-World Impact
Worst Case
Malicious insider or compromised account could manipulate channel membership to disrupt team collaboration, expose sensitive channel content to unauthorized users, or remove legitimate users from critical channels.
Likely Case
Accidental or intentional misuse by users with playbook access to modify channel memberships they shouldn't control, potentially causing minor collaboration disruptions.
If Mitigated
With proper access controls and monitoring, impact is limited to authorized users making unintended changes that can be quickly detected and reverted.
🎯 Exploit Status
Exploitation requires authenticated access and knowledge of playbook/channel relationships. No public exploit code known at this time.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 10.5.6, 9.11.16, 10.8.1, 10.7.3, 10.6.6
Vendor Advisory: https://mattermost.com/security-updates
Restart Required: Yes
Instructions:
1. Backup your Mattermost instance. 2. Upgrade to patched version: 10.5.6, 9.11.16, 10.8.1, 10.7.3, or 10.6.6. 3. Restart Mattermost service. 4. Verify version update.
🔧 Temporary Workarounds
Disable Playbooks Plugin
allTemporarily disable Mattermost Playbooks plugin to prevent exploitation
mmctl plugin disable com.mattermost.plugin-playbooks
Restrict Playbook Permissions
allLimit playbook creation and run permissions to trusted administrators only
Configure via System Console > Permissions > Playbooks
🧯 If You Can't Patch
- Implement strict monitoring of channel membership changes and playbook run activities
- Review and audit all user permissions, especially for users with playbook access
🔍 How to Verify
Check if Vulnerable:
Check Mattermost version via System Console > About or run: mmctl versionCheck Version:
mmctl versionVerify Fix Applied:
Verify version is 10.5.6, 9.11.16, 10.8.1, 10.7.3, or 10.6.6 or higher📡 Detection & Monitoring
Log Indicators:
- Unexpected channel membership changes
- Playbook run participant modifications without corresponding permission changes
- User added/removed from channel events
Network Indicators:
- API calls to modify playbook run participants followed by channel membership changes
SIEM Query:
source="mattermost" AND (event="api_channel_add_member" OR event="api_channel_remove_member") AND NOT user_has_permission="manage_channel_members"