CVE-2025-62176
📋 TL;DR
Mastodon's streaming server incorrectly allows OAuth clients with valid authentication tokens to subscribe to public timeline events even when those tokens lack the required read:statuses scope. This allows unauthorized access to new public posts in limited-federation settings. Only Mastodon instances running vulnerable versions are affected.
💻 Affected Systems
- Mastodon
📦 What is this software?
Mastodon by Joinmastodon
Mastodon by Joinmastodon
Mastodon by Joinmastodon
⚠️ Risk & Real-World Impact
Worst Case
Malicious OAuth clients could monitor all new public posts across federated instances in real-time without proper authorization, potentially enabling surveillance or data harvesting.
Likely Case
Accidental or unintended access to public timeline events by OAuth clients that shouldn't have read permissions, potentially violating access control policies.
If Mitigated
Limited to monitoring only new public posts (not historical data) and requires a valid authentication token, reducing overall impact.
🎯 Exploit Status
Requires obtaining a valid OAuth token (though without read:statuses scope) and understanding Mastodon's streaming API. No public exploit code available.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 4.4.6, 4.3.14, or 4.2.27
Vendor Advisory: https://github.com/mastodon/mastodon/security/advisories/GHSA-7gwh-mw97-qjgp
Restart Required: No
Instructions:
1. Backup your Mastodon instance. 2. Update to the patched version using your preferred method (git pull, package manager, or Docker). 3. Run database migrations if required. 4. Restart Mastodon services.
🔧 Temporary Workarounds
No workarounds available
allThe vendor advisory states no known workarounds exist. Patching is the only solution.
🧯 If You Can't Patch
- Disable the streaming server functionality if not required (may break real-time features).
- Implement network-level restrictions to limit access to streaming endpoints to trusted clients only.
🔍 How to Verify
Check if Vulnerable:
Check your Mastodon version. If it's earlier than 4.4.6, 4.3.14, or 4.2.27, you are vulnerable.Check Version:
RAILS_ENV=production bundle exec rails runner 'puts Mastodon::Version.to_s'Verify Fix Applied:
Confirm your Mastodon version is 4.4.6, 4.3.14, or 4.2.27 or later. Test that OAuth tokens without read:statuses scope cannot subscribe to public timeline events.📡 Detection & Monitoring
Log Indicators:
- Unusual streaming API requests from OAuth clients without read:statuses scope.
- Multiple failed authorization attempts followed by successful streaming connections.
Network Indicators:
- Unexpected connections to streaming endpoints (/api/v1/streaming) from unauthorized clients.
- High volume of WebSocket connections to public timeline endpoints.
SIEM Query:
source="mastodon.log" AND ("streaming" OR "/api/v1/streaming") AND NOT "scope=read:statuses"