CVE-2020-35970
📋 TL;DR
This CVE describes a Server-Side Request Forgery (SSRF) vulnerability in YzmCMS 5.8's background collection management feature. It allows authenticated attackers to read arbitrary files from the server, potentially exposing sensitive data. Only YzmCMS administrators with access to the vulnerable background management interface are affected.
💻 Affected Systems
- YzmCMS
📦 What is this software?
Yzmcms by Yzmcms
⚠️ Risk & Real-World Impact
Worst Case
Attackers could read sensitive server files like configuration files, password files, or source code, leading to complete system compromise through credential theft or further exploitation.
Likely Case
Authenticated administrators could abuse the vulnerability to read internal files, potentially accessing sensitive application data or configuration information.
If Mitigated
With proper access controls and network segmentation, impact would be limited to reading files accessible to the web server process only.
🎯 Exploit Status
Exploitation requires authenticated access to the vulnerable background management interface. The GitHub issue shows proof of concept details.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Versions after 5.8
Vendor Advisory: https://github.com/yzmcms/yzmcms/issues/53
Restart Required: No
Instructions:
1. Upgrade to the latest version of YzmCMS. 2. Apply any available security patches from the vendor. 3. Verify the collection management feature no longer accepts arbitrary file paths.
🔧 Temporary Workarounds
Restrict Background Access
allLimit access to the background management interface to trusted IP addresses only
# Configure web server (Apache/Nginx) to restrict /admin/ path to specific IPs
# Example Nginx: allow 192.168.1.0/24; deny all;
Disable Collection Feature
allTemporarily disable the vulnerable collection management feature
# Remove or rename the collection management module files
# Or disable via application configuration if available
🧯 If You Can't Patch
- Implement strict network segmentation to isolate the YzmCMS server from sensitive internal resources
- Deploy a web application firewall (WAF) with SSRF protection rules
🔍 How to Verify
Check if Vulnerable:
Check if running YzmCMS version 5.8 and test the collection management feature for file read capability using controlled test pathsCheck Version:
Check YzmCMS version in admin panel or look for version information in source filesVerify Fix Applied:
After patching, attempt to exploit the vulnerability with the same test paths and verify file reads are blocked📡 Detection & Monitoring
Log Indicators:
- Unusual file path requests in collection management logs
- Multiple failed file read attempts from background interface
- Access to sensitive file paths from web application
Network Indicators:
- Outbound requests from web server to internal services initiated via collection feature
- Unusual file:// protocol usage in HTTP requests
SIEM Query:
source="yzmcms.log" AND (path="file://" OR path="../../" OR path="/etc/")