CVE-2020-3938
📋 TL;DR
CVE-2020-3938 is a server-side request forgery (SSRF) vulnerability in SysJust Syuan-Gu-Da-Shih software that allows attackers to send forged requests from the vulnerable server to internal systems. This enables attackers to probe network architecture and access system files that should be inaccessible. Organizations using SysJust Syuan-Gu-Da-Shih versions before 20191223 are affected.
💻 Affected Systems
- SysJust Syuan-Gu-Da-Shih
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Attackers gain full access to internal network resources, sensitive system files, and potentially pivot to other critical systems, leading to data exfiltration or complete network compromise.
Likely Case
Attackers map internal network architecture, access configuration files, and potentially retrieve sensitive information from internal services.
If Mitigated
Limited to unsuccessful reconnaissance attempts with proper network segmentation and input validation in place.
🎯 Exploit Status
SSRF vulnerabilities typically require minimal technical skill to exploit once the attack vector is identified.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 20191223 or later
Vendor Advisory: https://tvn.twcert.org.tw/taiwanvn/TVN-201910014
Restart Required: Yes
Instructions:
1. Download the latest version from the vendor. 2. Backup current configuration. 3. Install the update. 4. Restart the service. 5. Verify the update was successful.
🔧 Temporary Workarounds
Network Segmentation
allRestrict outbound network access from the vulnerable server to only necessary internal services.
Input Validation
allImplement strict URL validation and whitelist allowed domains in the application configuration.
🧯 If You Can't Patch
- Implement strict network firewall rules to limit the server's outbound connections
- Deploy a web application firewall (WAF) with SSRF protection rules
🔍 How to Verify
Check if Vulnerable:
Check the software version in the administration interface or configuration files. If version is earlier than 20191223, the system is vulnerable.Check Version:
Check the application's admin panel or configuration files for version informationVerify Fix Applied:
Confirm the version is 20191223 or later and test that the application properly validates and restricts URL requests.📡 Detection & Monitoring
Log Indicators:
- Unusual outbound HTTP requests from the server to internal IP addresses
- Requests to file://, gopher://, or other unusual URI schemes
Network Indicators:
- Unexpected HTTP traffic from the vulnerable server to internal network segments
- Requests to metadata services (169.254.169.254)
SIEM Query:
source_ip=[vulnerable_server_ip] AND (dest_ip=10.* OR dest_ip=172.16.* OR dest_ip=192.168.* OR dest_ip=169.254.169.254) AND protocol=HTTP