CVE-2025-20036
📋 TL;DR
Mattermost Mobile Apps versions up to 2.22.0 fail to properly validate post properties, allowing authenticated malicious users to send specially crafted posts that crash the mobile application. This affects all users of vulnerable Mattermost mobile apps on Android and iOS platforms.
💻 Affected Systems
- Mattermost Mobile App for Android
- Mattermost Mobile App for iOS
📦 What is this software?
Mattermost Mobile by Mattermost
⚠️ Risk & Real-World Impact
Worst Case
An attacker could cause persistent denial-of-service for mobile users by repeatedly crashing their Mattermost apps, disrupting team communication and productivity.
Likely Case
Malicious users could temporarily disrupt specific users' mobile access to Mattermost by sending crash-inducing posts to channels or direct messages.
If Mitigated
With proper access controls and monitoring, impact is limited to temporary app crashes for targeted users until they restart the app.
🎯 Exploit Status
Exploitation requires authenticated access to create posts. The vulnerability is in post property validation, making exploitation straightforward once the malicious payload is known.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 2.23.0
Vendor Advisory: https://mattermost.com/security-updates
Restart Required: Yes
Instructions:
1. Update Mattermost Mobile App from official app stores (Google Play Store or Apple App Store). 2. For enterprise deployments, push updated app version through MDM solutions. 3. Verify all mobile clients are running version 2.23.0 or higher.
🔧 Temporary Workarounds
Restrict Post Creation Permissions
allTemporarily restrict post creation to trusted users only while updating mobile apps.
Web App Usage
allInstruct users to use Mattermost web interface instead of mobile apps until updates are deployed.
🧯 If You Can't Patch
- Monitor for unusual post patterns and user reports of app crashes
- Implement stricter user access controls and review user permissions
🔍 How to Verify
Check if Vulnerable:
Check mobile app version in app settings: Settings > About > Version. If version is 2.22.0 or lower, the app is vulnerable.Check Version:
Not applicable - check version through mobile app UI settingsVerify Fix Applied:
Verify mobile app version shows 2.23.0 or higher in app settings after update.📡 Detection & Monitoring
Log Indicators:
- Multiple app crash reports from same users
- Unusual post creation patterns from specific users
Network Indicators:
- Sudden drops in mobile app connections following specific posts
SIEM Query:
source="mattermost" AND (event="app_crash" OR message="*crash*" OR severity="error")