CVE-2021-26617
📋 TL;DR
CVE-2021-26617 is an input validation vulnerability in Firstmall that allows remote attackers to execute arbitrary code via the navercheckout_add function. This affects Firstmall e-commerce platforms with insufficient input validation. Attackers can exploit this without authentication to compromise affected systems.
💻 Affected Systems
- Firstmall
📦 What is this software?
Firstmall by Firstmall
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise with remote code execution leading to data theft, ransomware deployment, or lateral movement within the network.
Likely Case
Unauthenticated attackers executing malicious code to deface websites, steal customer data, or install backdoors for persistent access.
If Mitigated
Attack blocked at network perimeter with WAF rules or input validation, limiting impact to attempted exploitation logs.
🎯 Exploit Status
Vulnerability allows remote unauthenticated exploitation via crafted input to navercheckout_add function.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Not specified in references - check vendor advisory for exact version.
Vendor Advisory: https://www.krcert.or.kr/krcert/secNoticeView.do?bulletin_writing_sequence=36469
Restart Required: Yes
Instructions:
1. Contact Firstmall vendor for patch details. 2. Apply the security patch provided by the vendor. 3. Restart the Firstmall application/service. 4. Verify the patch is applied correctly.
🔧 Temporary Workarounds
Input Validation WAF Rule
allImplement web application firewall rules to validate and sanitize input to navercheckout_add function.
WAF-specific configuration required - no universal command
Function Disablement
allTemporarily disable or restrict access to the navercheckout_add function if not critical for business operations.
Application-specific configuration - consult Firstmall documentation
🧯 If You Can't Patch
- Implement strict input validation at application layer for all user inputs.
- Isolate affected systems in segmented network zones with strict access controls.
🔍 How to Verify
Check if Vulnerable:
Check if Firstmall version matches vulnerable versions from vendor advisory. Test input validation on navercheckout_add function.Check Version:
Application-specific - check Firstmall admin panel or configuration files for version information.Verify Fix Applied:
Verify patch version matches vendor's fixed version. Test that malicious input to navercheckout_add function is properly rejected.📡 Detection & Monitoring
Log Indicators:
- Unusual requests to navercheckout_add function with suspicious payloads
- Error logs showing input validation failures
- Unexpected process execution or file writes
Network Indicators:
- HTTP requests containing shell commands or encoded payloads targeting navercheckout_add endpoint
- Unusual outbound connections from Firstmall server
SIEM Query:
source="firstmall_logs" AND (uri="*navercheckout_add*" AND (payload="*cmd*" OR payload="*bash*" OR payload="*powershell*"))