CVE-2021-40954
📋 TL;DR
Laiketui 3.5.0 contains an arbitrary file upload vulnerability that allows attackers to upload malicious files to the server. This can lead to remote code execution, potentially compromising the entire system. Any organization using Laiketui 3.5.0 is affected.
💻 Affected Systems
- Laiketui
📦 What is this software?
Laiketui by Laiketui
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise with attacker gaining full control over the server, data theft, ransomware deployment, and lateral movement to other systems.
Likely Case
Webshell deployment leading to data exfiltration, credential harvesting, and use as a foothold for further attacks.
If Mitigated
Attack blocked at web application firewall level with no file uploads reaching vulnerable code.
🎯 Exploit Status
The vulnerability is well-documented in public GitHub issues with technical details that could be weaponized. File upload vulnerabilities are commonly exploited.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: No official vendor advisory found
Restart Required: No
Instructions:
Check GitHub repository for updates. Consider upgrading to newer versions if available. Review the GitHub issue for community patches or workarounds.
🔧 Temporary Workarounds
File Upload Restriction
allImplement strict file upload validation including file type checking, content verification, and size limits.
Implement server-side validation for file uploads
Restrict uploads to specific file extensions
Scan uploaded files for malicious content
Web Application Firewall Rules
allDeploy WAF rules to block malicious file upload attempts and suspicious POST requests.
Configure WAF to block file uploads with executable extensions
Implement rate limiting on upload endpoints
Add rules to detect webshell patterns
🧯 If You Can't Patch
- Isolate the Laiketui instance in a segmented network with strict outbound firewall rules
- Implement application-level monitoring for file upload activities and alert on suspicious patterns
🔍 How to Verify
Check if Vulnerable:
Check if running Laiketui version 3.5.0. Test file upload functionality with various file types to see if restrictions are bypassed.Check Version:
Check Laiketui configuration files or admin interface for version informationVerify Fix Applied:
Attempt to upload malicious files after implementing controls. Verify uploads are properly validated and rejected.📡 Detection & Monitoring
Log Indicators:
- Unusual file uploads with executable extensions
- Multiple failed upload attempts
- POST requests to upload endpoints with suspicious payloads
Network Indicators:
- HTTP POST requests with file uploads to Laiketui endpoints
- Outbound connections from Laiketui server to unknown IPs
SIEM Query:
source="web_server" AND (uri="*upload*" OR uri="*file*" OR method="POST") AND (extension="php" OR extension="jsp" OR extension="asp" OR extension="exe")