CVE-2020-21662
📋 TL;DR
This is a critical SQL injection vulnerability in YunyeCMS 2.0.2 that allows remote attackers to execute arbitrary SQL commands via the X-Forwarded-For (XFF) HTTP header. Attackers can potentially read, modify, or delete database content, and in some cases achieve remote code execution. Any system running the vulnerable YunyeCMS version is affected.
💻 Affected Systems
- YunyeCMS
📦 What is this software?
Yunyecms by Yunyecms
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of the database including data theft, data destruction, and potential remote code execution leading to full system takeover.
Likely Case
Database information disclosure, authentication bypass, privilege escalation, and potential website defacement.
If Mitigated
Limited impact with proper input validation, parameterized queries, and web application firewall rules blocking suspicious XFF headers.
🎯 Exploit Status
SQL injection via XFF header is a well-known attack vector with readily available exploitation tools.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: No official vendor advisory found
Restart Required: No
Instructions:
1. Check for official patches from YunyeCMS developers
2. If no patch available, consider migrating to alternative CMS
3. Apply workarounds and mitigations immediately
🔧 Temporary Workarounds
Web Application Firewall Rule
allBlock or sanitize X-Forwarded-For headers containing SQL injection patterns
# Example ModSecurity rule:
SecRule REQUEST_HEADERS:X-Forwarded-For "@rx (?i:(union.*select|insert.*into|update.*set|delete.*from|drop|truncate|exec|xp_cmdshell))" \
"id:1001,phase:2,deny,status:403,msg:'SQLi attempt via XFF header',logdata:'%{MATCHED_VAR}'
Input Validation Filter
allImplement server-side filtering of XFF headers to remove SQL special characters
# PHP example:
$xff = $_SERVER['HTTP_X_FORWARDED_FOR'] ?? '';
$clean_xff = preg_replace('/[^a-zA-Z0-9\.\-\:,\s]/', '', $xff);
🧯 If You Can't Patch
- Implement network segmentation to isolate the vulnerable system from critical assets
- Deploy a web application firewall with SQL injection detection rules
🔍 How to Verify
Check if Vulnerable:
Test by sending SQL injection payloads in X-Forwarded-For header and observing database errors or unexpected behaviorCheck Version:
Check YunyeCMS version in admin panel or look for version files in installation directoryVerify Fix Applied:
Test with SQL injection payloads in XFF header and verify they are blocked or sanitized without affecting functionality📡 Detection & Monitoring
Log Indicators:
- SQL syntax errors in application logs
- Unusual database queries from web server IP
- Multiple failed login attempts with SQL patterns in XFF header
Network Indicators:
- HTTP requests with SQL keywords in X-Forwarded-For header
- Abnormal database traffic patterns from web server
SIEM Query:
source="web_logs" AND (http_header="X-Forwarded-For" AND ("union select" OR "insert into" OR "update set" OR "delete from" OR xp_cmdshell OR "' OR '1'='1"))