CVE-2020-5505
📋 TL;DR
CVE-2020-5505 allows remote attackers to execute arbitrary commands on Freelancy v1.0.0 servers by sending specially crafted requests to the /api/files/ endpoint. This affects all users running the vulnerable version of Freelancy without proper input validation.
💻 Affected Systems
- Freelancy
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Full system compromise allowing attacker to execute arbitrary commands with web server privileges, potentially leading to data theft, system takeover, or lateral movement.
Likely Case
Remote code execution leading to web shell installation, data exfiltration, or cryptocurrency mining malware deployment.
If Mitigated
Attack blocked at network perimeter or by input validation, resulting in failed exploitation attempts.
🎯 Exploit Status
Exploit requires sending HTTP POST request with specific parameters to vulnerable endpoint.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: None available
Vendor Advisory: None available
Restart Required: No
Instructions:
No official patch exists. Upgrade to newer version if available or implement workarounds.
🔧 Temporary Workarounds
Input Validation Filter
allAdd input validation to reject requests containing PHP base64 data in file parameter
Implement server-side validation to block 'data:application/x-php;base64' in file uploads
WAF Rule
allBlock requests to /api/files/ containing PHP base64 data patterns
Add WAF rule: Block if request contains 'data:application/x-php;base64' AND 'type':'application/x-php'
🧯 If You Can't Patch
- Block access to /api/files/ endpoint at network perimeter
- Implement strict input validation and sanitization for all file upload functionality
🔍 How to Verify
Check if Vulnerable:
Check if Freelancy version is 1.0.0 and /api/files/ endpoint accepts file uploadsCheck Version:
Check application configuration or package manager for Freelancy versionVerify Fix Applied:
Test if /api/files/ endpoint rejects requests with 'data:application/x-php;base64' in file parameter📡 Detection & Monitoring
Log Indicators:
- HTTP POST requests to /api/files/ with base64 encoded PHP content
- Unusual file upload patterns to API endpoints
Network Indicators:
- POST requests containing 'data:application/x-php;base64' string
- Traffic to /api/files/ with unusual payloads
SIEM Query:
source="web_logs" AND uri="/api/files/" AND (request_body CONTAINS "data:application/x-php;base64" OR request_body CONTAINS "type":"application/x-php")