CVE-2018-1000059
📋 TL;DR
CVE-2018-1000059 is a PHP object injection vulnerability in ValidFormBuilder's unserialize method that allows remote attackers to execute arbitrary system commands and read files. This affects websites using ValidFormBuilder 4.5.4 for form processing. Attackers can achieve remote code execution without authentication.
💻 Affected Systems
- ValidFormBuilder
📦 What is this software?
Validform Builder by Validformbuilder
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise allowing remote attackers to execute arbitrary commands, read sensitive files, install backdoors, and pivot to other systems.
Likely Case
Remote code execution leading to website defacement, data theft, or cryptocurrency mining malware installation.
If Mitigated
Limited impact if proper input validation and output encoding are implemented, though the core vulnerability remains.
🎯 Exploit Status
Exploitation is straightforward once the vulnerable endpoint is identified; public proof-of-concept code exists.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Version 4.5.5 or later
Vendor Advisory: https://github.com/validformbuilder/validformbuilder/issues/126
Restart Required: No
Instructions:
1. Update ValidFormBuilder to version 4.5.5 or later. 2. Replace the vulnerable unserialize method with secure alternatives. 3. Test form functionality after update.
🔧 Temporary Workarounds
Input Validation Filter
allImplement strict input validation to reject serialized data in form submissions
// PHP code to validate form input
if (preg_match('/[Oa]:\d+:/', $input)) {
die('Invalid input detected');
}
WAF Rule
linuxDeploy web application firewall rules to block serialized object patterns
# Example ModSecurity rule
SecRule ARGS "@rx [Oa]:\d+:" "id:1000059,phase:2,deny,msg:'CVE-2018-1000059 exploit attempt'"
🧯 If You Can't Patch
- Disable or remove ValidFormBuilder from production systems
- Implement network segmentation to isolate affected systems and restrict access
🔍 How to Verify
Check if Vulnerable:
Check if ValidFormBuilder version 4.5.4 is installed by examining the software version in the codebase or package manager.Check Version:
grep -r "ValidFormBuilder" /path/to/webroot/ | grep -i versionVerify Fix Applied:
Verify the version is updated to 4.5.5 or later and test form submission functionality.📡 Detection & Monitoring
Log Indicators:
- Unusual POST requests to form processing endpoints
- PHP unserialize errors in application logs
- Suspicious file read or system command execution attempts
Network Indicators:
- HTTP requests containing serialized object patterns (O:8:, a:5:, etc.)
- Outbound connections from web server to unexpected destinations
SIEM Query:
source="web_logs" AND (url="*form*process*" OR url="*validform*") AND (request_body="*O:*" OR request_body="*a:*")