CVE-2025-29843
📋 TL;DR
This vulnerability in Synology FileStation's thumb.cgi component allows authenticated users to read and write image files they shouldn't have access to. It affects Synology NAS devices running DSM with FileStation enabled. Attackers need valid credentials but can then access or modify sensitive image files.
💻 Affected Systems
- Synology DiskStation Manager (DSM)
- Synology FileStation
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
An authenticated attacker could read sensitive image files containing confidential information or overwrite critical system images, potentially causing data loss or service disruption.
Likely Case
An authenticated user with malicious intent could access private image files belonging to other users or modify shared image content.
If Mitigated
With proper access controls and monitoring, impact is limited to unauthorized access to image files within the authenticated user's privilege scope.
🎯 Exploit Status
Exploitation requires authenticated access. The vulnerability is in thumb.cgi parameter handling.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: DSM 7.2-64570 Update 1 and later
Vendor Advisory: https://www.synology.com/en-global/security/advisory/Synology_SA_25_04
Restart Required: No
Instructions:
1. Log into DSM as administrator. 2. Go to Control Panel > Update & Restore. 3. Check for updates. 4. Install DSM 7.2-64570 Update 1 or later. 5. Verify update completes successfully.
🔧 Temporary Workarounds
Disable FileStation
allTemporarily disable FileStation service to prevent exploitation
Go to Control Panel > Application Portal > File Station > Uncheck 'Enable File Station'
Restrict FileStation Access
allLimit FileStation access to trusted IP addresses only
Go to Control Panel > Security > Firewall > Create rule to restrict FileStation ports (5000, 5001) to trusted IPs
🧯 If You Can't Patch
- Implement strict access controls and monitor FileStation access logs for suspicious activity
- Disable FileStation for users who don't require it and implement network segmentation
🔍 How to Verify
Check if Vulnerable:
Check DSM version in Control Panel > Info Center. If version is earlier than DSM 7.2-64570 Update 1 and FileStation is enabled, system is vulnerable.Check Version:
ssh admin@nas_ip 'cat /etc.defaults/VERSION'Verify Fix Applied:
Verify DSM version is 7.2-64570 Update 1 or later in Control Panel > Info Center.📡 Detection & Monitoring
Log Indicators:
- Unusual thumb.cgi requests with file path manipulation
- Multiple failed authentication attempts followed by thumb.cgi access
- Access to image files outside user's normal directory patterns
Network Indicators:
- HTTP requests to /webapi/entry.cgi with thumb.cgi parameters
- Unusual file access patterns via FileStation API
SIEM Query:
source="synology" AND (uri="*thumb.cgi*" OR uri="*entry.cgi*" AND params="*thumb*" AND (params="*..*" OR params="*%2e%2e*"))