CVE-2020-20948
📋 TL;DR
CVE-2020-20948 is an arbitrary file download vulnerability in JEECG v3.8 that allows attackers to access sensitive server files by manipulating the 'localPath' parameter. This affects all systems running vulnerable JEECG versions, potentially exposing configuration files, credentials, and other sensitive data.
💻 Affected Systems
- JEECG
📦 What is this software?
Jeecg by Jeecg
⚠️ Risk & Real-World Impact
Worst Case
Complete server compromise through retrieval of configuration files containing database credentials, SSH keys, or other authentication secrets leading to lateral movement and data exfiltration.
Likely Case
Exposure of sensitive configuration files, source code, and potentially credentials stored in accessible file paths.
If Mitigated
Limited impact with proper file system permissions and network segmentation preventing access to critical system files.
🎯 Exploit Status
Simple parameter manipulation attack requiring minimal technical skill. Public GitHub issues demonstrate the vulnerability.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: v3.8.1 or later
Vendor Advisory: https://github.com/zhangdaiscott/jeecg/issues/50
Restart Required: Yes
Instructions:
1. Upgrade JEECG to version 3.8.1 or later. 2. Apply security patches from the JEECG repository. 3. Restart the application server.
🔧 Temporary Workarounds
Input Validation Filter
allImplement server-side validation to restrict file paths to allowed directories only
Implement path traversal filters in file download servlets
Validate 'localPath' parameter against whitelist of allowed paths
Web Application Firewall Rules
allBlock requests containing directory traversal sequences in parameters
WAF rule: block requests with '../' or '..\' in URL parameters
Block requests attempting to access sensitive file extensions (.properties, .xml, .conf)
🧯 If You Can't Patch
- Implement strict file system permissions to limit web application user access to only necessary directories
- Deploy network segmentation to isolate JEECG instances from sensitive systems and databases
🔍 How to Verify
Check if Vulnerable:
Test by attempting to download files outside allowed directories using path traversal in the localPath parameter (e.g., ../../etc/passwd)Check Version:
Check JEECG version in application properties or via version endpoint if availableVerify Fix Applied:
Attempt the same path traversal attacks after patching - they should be blocked or return error messages📡 Detection & Monitoring
Log Indicators:
- Multiple failed file access attempts with path traversal patterns
- Access to sensitive file paths in web server logs
- Unusual file download patterns from single IP
Network Indicators:
- HTTP requests with '../' sequences in parameters
- Requests for known sensitive files (passwd, shadow, config files)
SIEM Query:
web.url:*../* AND (web.url:*.properties OR web.url:*.xml OR web.url:*.conf) AND status:200