CVE-2026-1046
📋 TL;DR
This vulnerability allows a malicious Mattermost server to execute arbitrary executables on a user's system when the user clicks on certain items in the Help menu. The issue affects Mattermost Desktop App users who connect to untrusted or compromised servers. Attackers can achieve remote code execution through social engineering.
💻 Affected Systems
- Mattermost Desktop App
⚠️ Manual Verification Required
This CVE does not have specific version information in our database, so automatic vulnerability detection cannot determine if your system is affected.
Why? The CVE database entry doesn't specify which versions are vulnerable (no version ranges provided by the vendor/NVD).
🔒 Custom verification scripts are available for registered users. Sign up free to download automated test scripts.
- Review the CVE details at NVD
- Check vendor security advisories for your specific version
- Test if the vulnerability is exploitable in your environment
- Consider updating to the latest version as a precaution
⚠️ Risk & Real-World Impact
Worst Case
Full system compromise with attacker gaining complete control over the user's machine, leading to data theft, ransomware deployment, or lateral movement within the network.
Likely Case
Malicious server operators execute malware or steal sensitive data from users who click on help menu items, potentially affecting multiple users in an organization.
If Mitigated
Limited impact with proper server trust controls and user awareness, potentially only affecting isolated systems with no critical data.
🎯 Exploit Status
Exploitation requires server-side control and user interaction. The attack vector is straightforward once server compromise occurs.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Versions after 6.0, 6.2.0, and 5.2.13.0 (check Mattermost security updates for exact fixed versions)
Vendor Advisory: https://mattermost.com/security-updates
Restart Required: Yes
Instructions:
1. Visit https://mattermost.com/download 2. Download latest desktop app version 3. Install over existing installation 4. Restart the application
🔧 Temporary Workarounds
Disable Help Menu Access
allPrevent users from accessing the Help menu to block the attack vector
Not applicable - configuration change
Restrict Server Connections
allOnly allow connections to trusted Mattermost servers
Not applicable - policy enforcement
🧯 If You Can't Patch
- Implement network segmentation to isolate Mattermost traffic and prevent lateral movement
- Deploy application control/whitelisting to prevent unauthorized executable execution
🔍 How to Verify
Check if Vulnerable:
Check Mattermost Desktop App version in Help > About. If version is <=6.0, 6.2.0, or 5.2.13.0, system is vulnerable.Check Version:
On Mattermost Desktop: Click Help > AboutVerify Fix Applied:
After updating, verify version in Help > About shows a version higher than affected versions.📡 Detection & Monitoring
Log Indicators:
- Unexpected process execution from Mattermost directory
- Help menu access logs showing unusual patterns
Network Indicators:
- Connections to untrusted Mattermost servers
- Unexpected outbound connections after help menu interaction
SIEM Query:
Process Creation where Image contains 'mattermost' AND CommandLine contains unusual parameters OR ParentProcess contains 'mattermost'