CVE-2025-62690
📋 TL;DR
Mattermost versions 10.11.4 and earlier contain an open redirect vulnerability on the /error page. An attacker can craft a malicious link that redirects victims to arbitrary websites when opened in a new tab. This affects all Mattermost deployments running vulnerable versions.
💻 Affected Systems
- Mattermost
📦 What is this software?
Mattermost Server by Mattermost
⚠️ Risk & Real-World Impact
Worst Case
Users could be redirected to phishing sites that steal credentials or deliver malware, potentially leading to account compromise or system infection.
Likely Case
Phishing attacks where users are tricked into visiting malicious sites that appear legitimate due to the Mattermost domain in the initial URL.
If Mitigated
Limited impact with proper user awareness training and browser security controls that warn about suspicious redirects.
🎯 Exploit Status
Exploitation requires user interaction (clicking a crafted link) but no authentication to Mattermost.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 10.11.5 or later
Vendor Advisory: https://mattermost.com/security-updates
Restart Required: Yes
Instructions:
1. Backup your Mattermost installation and database. 2. Download Mattermost version 10.11.5 or later from the official website. 3. Stop the Mattermost service. 4. Replace the installation with the patched version. 5. Restart the Mattermost service. 6. Verify the upgrade was successful.
🔧 Temporary Workarounds
User Awareness Training
allEducate users about phishing risks and not clicking suspicious links, especially those that open in new tabs.
Browser Security Controls
allEnable browser security features that warn about or block suspicious redirects.
🧯 If You Can't Patch
- Implement web application firewall rules to block suspicious redirect patterns from the /error endpoint.
- Monitor for unusual redirect activity in Mattermost access logs.
🔍 How to Verify
Check if Vulnerable:
Check Mattermost version via System Console > About or run: grep -i version /opt/mattermost/config/config.jsonCheck Version:
grep -i version /opt/mattermost/config/config.jsonVerify Fix Applied:
Confirm version is 10.11.5 or later and test that crafted redirect URLs to the /error page no longer work.📡 Detection & Monitoring
Log Indicators:
- Unusual access patterns to /error page with redirect parameters
- Multiple failed redirect attempts from same IP
Network Indicators:
- HTTP 302 redirects from Mattermost /error page to external domains
SIEM Query:
source="mattermost" AND url="/error" AND (status=302 OR redirect_to="*://*")