CVE-2026-4540: Online Notes Sharing System SQLi Flaw

CVE-2026-4540 Overview

A SQL injection vulnerability has been identified in projectworlds Online Notes Sharing System version 1.0. This issue affects the /login.php file within the Parameters Handler component. The vulnerability allows remote attackers to manipulate the User argument parameter to execute arbitrary SQL commands against the backend database. The exploit has been publicly disclosed and may be actively used by threat actors.

Critical Impact
Remote attackers can exploit this SQL injection flaw to bypass authentication, extract sensitive data, modify database contents, or potentially escalate to full system compromise through database server vulnerabilities.

Affected Products

projectworlds Online Notes Sharing System 1.0
Systems using vulnerable /login.php authentication endpoint
Web applications with exposed Parameters Handler component

Discovery Timeline

2026-03-22 - CVE-2026-4540 published to NVD
2026-03-23 - Last updated in NVD database

Technical Details for CVE-2026-4540

Vulnerability Analysis

This SQL injection vulnerability (CWE-74: Improper Neutralization of Special Elements in Output Used by a Downstream Component) exists in the login authentication mechanism of the Online Notes Sharing System. The application fails to properly sanitize user-supplied input in the User parameter before incorporating it into SQL queries. This allows attackers to inject malicious SQL statements that are executed by the database server with the same privileges as the application's database user.

The vulnerability is network-accessible and requires no authentication or user interaction to exploit. An attacker can craft malicious HTTP requests to the /login.php endpoint containing SQL injection payloads in the User parameter, potentially allowing unauthorized access to the application and its underlying data.

Root Cause

The root cause of this vulnerability is improper input validation and the use of unsanitized user input in SQL query construction. The application's Parameters Handler component does not implement proper input sanitization, parameterized queries, or prepared statements when processing the User argument. This allows SQL metacharacters and commands to be passed directly to the database engine.

Attack Vector

The attack is executed remotely over the network by sending specially crafted HTTP requests to the vulnerable /login.php endpoint. An attacker manipulates the User parameter to inject SQL syntax that alters the intended query logic. Common exploitation techniques include authentication bypass using tautologies (e.g., ' OR '1'='1), UNION-based data extraction, or time-based blind injection to enumerate database contents.

The vulnerability requires no prior authentication, making it accessible to any remote attacker who can reach the application's login page. Successful exploitation could lead to unauthorized access, data theft, or further compromise of the underlying server infrastructure.

Detection Methods for CVE-2026-4540

Indicators of Compromise

Unusual SQL error messages in application logs originating from /login.php
Anomalous login attempts with special characters or SQL syntax in username fields
Database audit logs showing unexpected queries or data access patterns
Multiple failed authentication attempts followed by successful access from the same source

Detection Strategies

Deploy Web Application Firewall (WAF) rules to detect SQL injection patterns in the User parameter
Monitor application logs for SQL syntax errors and injection signatures targeting /login.php
Implement database activity monitoring to detect anomalous query patterns
Configure intrusion detection systems (IDS) with SQL injection detection rules

Monitoring Recommendations

Enable detailed logging for all authentication attempts on the vulnerable endpoint
Set up alerts for requests containing SQL metacharacters (', ", ;, --, /*)
Monitor database server logs for unauthorized data access or privilege escalation attempts
Implement real-time analysis of HTTP request parameters for injection patterns

How to Mitigate CVE-2026-4540

Immediate Actions Required

Restrict network access to the vulnerable /login.php endpoint using firewall rules
Implement input validation to block SQL injection attempts at the web server level
Deploy a Web Application Firewall (WAF) with SQL injection protection rules
Consider taking the application offline until a proper fix can be implemented

Patch Information

No official vendor patch has been identified in the available CVE data. Organizations using this software should contact projectworlds for security updates or implement the workarounds described below. Additional technical details are available through the GitHub CVE Issue Discussion and VulDB #352357.

Workarounds

Implement parameterized queries or prepared statements for all database interactions in /login.php
Apply strict input validation using allowlist patterns for the User parameter
Deploy a reverse proxy or WAF with SQL injection filtering capabilities
Implement application-level input sanitization to escape SQL metacharacters
Consider disabling or restricting access to the affected component until patched

bash

# Example WAF rule configuration (ModSecurity)
# Block SQL injection attempts on login endpoint
SecRule REQUEST_URI "@contains /login.php" \
    "id:1001,phase:2,deny,status:403,log,\
    chain"
SecRule ARGS:User "@detectSQLi" \
    "t:none,t:urlDecodeUni,t:htmlEntityDecode"