CVE-2020-21653
📋 TL;DR
Myucms v2.2.1 contains a server-side request forgery (SSRF) vulnerability in the index.php controller's sj() method. This allows attackers to make arbitrary HTTP requests from the vulnerable server, potentially accessing internal systems or services. All users running Myucms v2.2.1 are affected.
💻 Affected Systems
- Myucms
📦 What is this software?
Myucms by Myucms Project
⚠️ Risk & Real-World Impact
Worst Case
Attackers could pivot to internal networks, access cloud metadata services, perform port scanning, or interact with internal APIs to steal sensitive data or execute further attacks.
Likely Case
Attackers would access internal services, scan internal networks, or interact with localhost services to gather information or perform limited actions.
If Mitigated
With proper network segmentation and egress filtering, impact would be limited to the local server environment only.
🎯 Exploit Status
The vulnerability is in a public method and requires minimal technical skill to exploit.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: Unknown
Restart Required: No
Instructions:
No official patch available. Consider upgrading to a newer version if available, or apply workarounds.
🔧 Temporary Workarounds
Input Validation and Sanitization
allAdd input validation to the sj() method to restrict URL parameters to allowed domains only.
Modify \controller\index.php to validate URL parameters before making requests
Network Egress Filtering
linuxImplement firewall rules to restrict outbound HTTP/HTTPS traffic from the web server to only necessary external services.
iptables -A OUTPUT -p tcp --dport 80 -j DROP
iptables -A OUTPUT -p tcp --dport 443 -j DROP
🧯 If You Can't Patch
- Implement web application firewall (WAF) rules to block SSRF patterns
- Isolate the vulnerable server in a restricted network segment
🔍 How to Verify
Check if Vulnerable:
Check if Myucms version is v2.2.1 by examining the application files or configuration.Check Version:
Check the application's version file or configuration settings.Verify Fix Applied:
Test the sj() method with SSRF payloads to ensure they are blocked or properly validated.📡 Detection & Monitoring
Log Indicators:
- Unusual outbound HTTP requests from the web server
- Requests to internal IP addresses or localhost from the web application
Network Indicators:
- HTTP requests from web server to unusual destinations
- Port scanning activity originating from the web server
SIEM Query:
source="web_server" AND (dest_ip="127.0.0.1" OR dest_ip="169.254.169.254" OR dest_ip="10.*" OR dest_ip="172.16.*" OR dest_ip="192.168.*")