CVE-2025-13324
📋 TL;DR
This vulnerability allows attackers who obtain remote cluster invite tokens to authenticate as remote clusters and perform limited actions on shared channels in Mattermost, even after legitimate invitation confirmation. It affects Mattermost servers using legacy protocol v1 or when confirming parties don't provide refreshed tokens. Organizations running affected Mattermost versions with remote cluster features enabled are vulnerable.
💻 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
An attacker could gain unauthorized access to shared channels, potentially accessing sensitive communications, manipulating channel content, or disrupting collaboration between federated Mattermost instances.
Likely Case
Limited unauthorized access to shared channels where the attacker can view messages, post content, or perform other channel-level actions they shouldn't have permission for.
If Mitigated
If proper network segmentation and access controls are in place, impact is limited to the specific shared channels the compromised token provides access to.
🎯 Exploit Status
Requires obtaining invite tokens through other means (social engineering, credential theft, etc.) and knowledge of the remote cluster setup.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 10.11.6, 11.0.5, 10.12.3 or later
Vendor Advisory: https://mattermost.com/security-updates
Restart Required: Yes
Instructions:
1. Backup your Mattermost configuration and database. 2. Download the patched version from Mattermost downloads page. 3. Stop the Mattermost service. 4. Install the updated version following Mattermost upgrade documentation. 5. Restart the Mattermost service. 6. Verify the upgrade was successful.
🔧 Temporary Workarounds
Disable Remote Cluster Features
allTemporarily disable remote cluster functionality if not required for operations
Set 'EnableRemoteClusterService' to false in config.json
Force Protocol v2
allConfigure all remote clusters to use protocol version 2
Update remote cluster configurations to use protocol version 2
🧯 If You Can't Patch
- Disable remote cluster functionality entirely if not business-critical
- Implement strict network segmentation to isolate Mattermost instances and monitor for unusual remote cluster authentication attempts
🔍 How to Verify
Check if Vulnerable:
Check Mattermost version via System Console > About or run 'mattermost version' command. Verify if using remote clusters with legacy protocol v1.Check Version:
mattermost versionVerify Fix Applied:
Confirm version is 10.11.6+, 11.0.5+, or 10.12.3+ and test remote cluster functionality works properly with protocol v2.📡 Detection & Monitoring
Log Indicators:
- Unusual remote cluster authentication attempts
- Multiple failed token validations
- Remote cluster access from unexpected IPs
Network Indicators:
- Unexpected traffic between Mattermost instances
- Authentication attempts using old/invalidated tokens
SIEM Query:
source="mattermost" AND ("remote cluster" OR "invite token") AND ("failed" OR "unauthorized")