CVE-2024-53863
📋 TL;DR
This vulnerability in Synapse Matrix homeserver allows attackers to trigger processing of uncommon image formats by enabling dynamic_thumbnails or sending crafted requests, potentially invoking external tools like Ghostscript. This significantly expands the attack surface in a historically vulnerable area. All Synapse instances with dynamic_thumbnails enabled or processing user-uploaded images are affected.
💻 Affected Systems
- Synapse Matrix homeserver
📦 What is this software?
Synapse by Matrix
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution through Ghostscript or other image processing tools, potentially leading to complete server compromise.
Likely Case
Denial of service through resource exhaustion or limited code execution via image processing tool vulnerabilities.
If Mitigated
Limited impact if external image processing tools are sandboxed and resource limits are enforced.
🎯 Exploit Status
Exploitation requires knowledge of uncommon image formats and ability to trigger thumbnail generation.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 1.120.1
Vendor Advisory: https://github.com/element-hq/synapse/security/advisories/GHSA-vp6v-whfm-rv3g
Restart Required: No
Instructions:
1. Update Synapse to version 1.120.1 or later using your package manager. 2. Verify the update completed successfully. 3. No restart required as Synapse automatically reloads configuration.
🔧 Temporary Workarounds
Disable dynamic_thumbnails
allDisable the dynamic_thumbnails option in Synapse configuration to prevent processing of uncommon image formats.
Edit homeserver.yaml and set: dynamic_thumbnails: false
🧯 If You Can't Patch
- Disable dynamic_thumbnails option in configuration
- Implement strict network controls to limit image upload sources
🔍 How to Verify
Check if Vulnerable:
Check Synapse version and if dynamic_thumbnails is enabled in homeserver.yamlCheck Version:
synctl --version or check Synapse logs for version informationVerify Fix Applied:
Verify Synapse version is 1.120.1 or later and check that thumbnail generation only processes PNG, JPEG, GIF, WebP formats📡 Detection & Monitoring
Log Indicators:
- Unusual image format processing in logs
- Ghostscript or other image tool invocation errors
- High resource usage during thumbnail generation
Network Indicators:
- Unusual image uploads with uncommon formats
- Requests triggering thumbnail generation for non-standard images
SIEM Query:
source="synapse.log" AND ("uncommon format" OR "Ghostscript" OR "thumbnail generation error")