CVE-2024-37303
📋 TL;DR
Synapse Matrix homeserver versions before 1.106 allow unauthenticated remote users to trigger downloads of remote media content and cache it locally, making that content available for unauthenticated download from the local server. This enables adversaries to plant problematic content in the media repository. All Synapse instances running vulnerable versions are affected.
💻 Affected Systems
- Synapse Matrix homeserver
📦 What is this software?
Synapse by Matrix
⚠️ Risk & Real-World Impact
Worst Case
Adversaries could upload malicious or illegal content to the media repository, potentially exposing the server operator to legal liability or reputational damage.
Likely Case
Attackers could use this to store and distribute inappropriate or malicious media files through the vulnerable server.
If Mitigated
With authentication required for media downloads, only authorized users can trigger media caching and access cached content.
🎯 Exploit Status
Exploitation requires only unauthenticated access to trigger media downloads from remote servers.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 1.106 and later
Vendor Advisory: https://github.com/element-hq/synapse/security/advisories/GHSA-gjgr-7834-rhxr
Restart Required: Yes
Instructions:
1. Update Synapse to version 1.106 or later using your package manager or installation method. 2. Restart the Synapse service. 3. Verify the update was successful.
🔧 Temporary Workarounds
Restrict media repository access
allImplement network-level restrictions to limit access to media endpoints from untrusted sources.
🧯 If You Can't Patch
- Implement strict network segmentation to isolate the Synapse server from untrusted networks.
- Deploy a web application firewall (WAF) to filter requests to media endpoints.
🔍 How to Verify
Check if Vulnerable:
Check Synapse version: if running version earlier than 1.106, the system is vulnerable.Check Version:
synctl --version or check synapse.__version__ in PythonVerify Fix Applied:
Confirm Synapse version is 1.106 or later and that authentication is required for media downloads.📡 Detection & Monitoring
Log Indicators:
- Unusual volume of media download requests from unauthenticated sources
- Requests to /_matrix/media/v1/download endpoint without authentication
Network Indicators:
- High volume of outbound requests to remote media servers triggered by unauthenticated clients
SIEM Query:
source="synapse.log" AND "_matrix/media/v1/download" AND NOT "authenticated_user_id"