CVE-2021-47918: Simple CMS 2.1 SQL Injection Vulnerability

CVE-2021-47918 Overview

CVE-2021-47918 is a remote SQL injection vulnerability affecting Simple CMS version 2.1. The vulnerability exists in the users module and allows privileged attackers to inject unfiltered SQL commands through the admin.php file. By exploiting unvalidated input parameters, attackers can compromise the underlying database management system and potentially the entire web application.

Critical Impact

Attackers with privileged access can execute arbitrary SQL commands, potentially leading to unauthorized data access, data manipulation, or complete database compromise.

Affected Products

• Simple CMS 2.1

Discovery Timeline

• 2026-02-01 - CVE CVE-2021-47918 published to NVD
• 2026-02-03 - Last updated in NVD database

Technical Details for CVE-2021-47918

Vulnerability Analysis

This vulnerability is classified under CWE-89 (Improper Neutralization of Special Elements used in an SQL Command), commonly known as SQL Injection. The flaw resides in the users module of Simple CMS 2.1, specifically within the admin.php file. The application fails to properly validate and sanitize user-supplied input before incorporating it into SQL queries, allowing attackers to manipulate database operations.

The network-based attack vector means that exploitation can occur remotely without requiring physical access to the target system. While the vulnerability requires some level of privileged access (authenticated session), the complexity of exploitation is low, making it accessible to attackers with basic SQL injection knowledge.

Root Cause

The root cause of CVE-2021-47918 is improper input validation in the admin.php file within the users module. The application directly incorporates user-controlled parameters into SQL queries without proper sanitization, parameterized queries, or prepared statements. This allows malicious SQL syntax to be interpreted by the database engine rather than being treated as literal data.

Attack Vector

The attack vector for this vulnerability is network-based, requiring an attacker to have authenticated access to the administrative interface. Once authenticated, an attacker can craft malicious input containing SQL syntax and submit it through the vulnerable parameters in the users module. The injected SQL commands are then executed by the database with the same privileges as the application's database connection.

The vulnerability allows attackers to potentially:

• Extract sensitive data from the database
• Modify or delete database records
• Bypass authentication mechanisms stored in the database
• Escalate privileges within the application

For detailed technical information about the exploitation mechanism, refer to the Vulnerability Lab #2303 advisory and the VulnCheck SQL Injection Advisory.

Detection Methods for CVE-2021-47918

Indicators of Compromise

• Unusual SQL syntax patterns in web server access logs targeting admin.php
• Database query logs showing unexpected UNION SELECT, OR 1=1, or other SQL injection signatures
• Unexplained database modifications or data exfiltration patterns
• Error messages in application logs indicating SQL syntax errors from malformed injection attempts

Detection Strategies

• Implement Web Application Firewall (WAF) rules to detect and block common SQL injection patterns
• Monitor access logs for suspicious requests to the users module in admin.php
• Deploy database activity monitoring to detect anomalous query patterns
• Enable verbose logging on the database server to capture all executed queries for forensic analysis

Monitoring Recommendations

• Configure real-time alerting for SQL injection signature patterns in web traffic
• Monitor database connection counts and query execution times for anomalies
• Implement audit logging for all administrative actions in Simple CMS
• Review authentication logs for unusual admin login patterns that may precede exploitation attempts

How to Mitigate CVE-2021-47918

Immediate Actions Required

• Restrict access to the Simple CMS administrative interface to trusted IP addresses only
• Implement additional authentication controls such as multi-factor authentication for admin access
• Deploy a Web Application Firewall with SQL injection protection rules
• Review and audit all administrative user accounts for unauthorized access

Patch Information

Users should check the Simple PHP Scripts CMS official website for any available security updates or patches addressing this vulnerability. If no patch is available, consider implementing the workarounds below or migrating to a more actively maintained CMS platform.

Workarounds

• Implement network-level access controls to restrict admin panel access to trusted networks only
• Use a reverse proxy with SQL injection filtering capabilities in front of the application
• Manually sanitize input parameters in the admin.php file if source code modification is possible
• Consider disabling or restricting the users module functionality until a patch is available
• Regularly backup database content to enable recovery in case of successful exploitation

# Example: Restrict admin.php access via .htaccess
# Place in the Simple CMS directory

<Files "admin.php">
    Order Deny,Allow
    Deny from all
    Allow from 192.168.1.0/24
    Allow from 10.0.0.0/8
</Files>