CVE-2021-26634
📋 TL;DR
CVE-2021-26634 is a critical vulnerability in Maxboard software that allows SQL injection and file upload attacks due to insufficient input validation. Attackers can exploit this to execute arbitrary code, escalate privileges, and potentially gain full server control via web shells. All organizations using vulnerable Maxboard versions are affected.
💻 Affected Systems
- Maxboard
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete server compromise leading to data theft, ransomware deployment, and persistent backdoor installation across the network.
Likely Case
Web shell installation enabling data exfiltration, lateral movement, and credential harvesting from the affected server.
If Mitigated
Limited impact with proper network segmentation and WAF rules blocking SQL injection patterns and file uploads to vulnerable endpoints.
🎯 Exploit Status
SQL injection combined with file upload makes exploitation straightforward for attackers with basic web application testing skills.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Not specified in references, but vendor has released security updates
Vendor Advisory: https://www.krcert.or.kr/krcert/secNoticeView.do?bulletin_writing_sequence=66746
Restart Required: Yes
Instructions:
1. Download latest Maxboard version from official vendor. 2. Backup current installation and data. 3. Apply patch/upgrade following vendor instructions. 4. Restart Maxboard service. 5. Verify fix implementation.
🔧 Temporary Workarounds
WAF Rule Implementation
allDeploy web application firewall rules to block SQL injection patterns and restrict file uploads to Maxboard endpoints
Input Validation Enhancement
allImplement additional input validation and sanitization at the application level for all user-supplied parameters
🧯 If You Can't Patch
- Isolate Maxboard server in separate network segment with strict firewall rules
- Implement application-level input validation and disable file upload functionality if not required
🔍 How to Verify
Check if Vulnerable:
Check Maxboard version against vendor advisory and test for SQL injection vulnerabilities in application parametersCheck Version:
Check Maxboard version through application interface or configuration files (specific command depends on installation)Verify Fix Applied:
Test previously vulnerable endpoints for SQL injection and file upload vulnerabilities after patch application📡 Detection & Monitoring
Log Indicators:
- Unusual SQL queries in application logs
- Unexpected file uploads to Maxboard directories
- Web shell file creation in web root
Network Indicators:
- SQL injection patterns in HTTP requests
- POST requests with file uploads to vulnerable endpoints
- Outbound connections from Maxboard server to unknown IPs
SIEM Query:
source="maxboard.log" AND ("union select" OR "1=1" OR ".php" OR ".jsp" OR ".asp" in uri)