CVE-2023-40944 shines a spotlight on a critical SQL injection vulnerability in Schoolmate 1.3, an open-source web application widely used by K-12 schools for student information management. This post will walk you through how the vulnerability occurs, exampling the affected code, and even demonstrating how an attack might look in practice. You’ll also find original references for further reading.

What is Schoolmate 1.3?

Schoolmate is a straightforward PHP/MySQL system for managing student data, grades, schedules, and more. It's popular because it's free and easy to set up, but older versions (like 1.3) have some security gaps.

CVSS (Predicted): 9.8 (Critical)

The $schoolname variable, as retrieved and used from the database in header.php, isn’t properly sanitized. That means an attacker can inject malicious SQL code that the database will execute.

Vulnerable Code Example

The vulnerable code can be found around lines where the application displays the name of the school at the top of the page. Typically, it looks like this:

<?php
include("Database.php"); // connect to the database

$q = "SELECT schoolname FROM schoolinfo";
$result = mysql_query($q);
$row = mysql_fetch_array($result);
$schoolname = $row['schoolname'];

// Display school name in header
echo "<h1>$schoolname</h1>";
?>

At first, this might look harmless, but there's a risky assumption: the value of $schoolname in the database may not be trusted. Without proper escaping or output filtering, the web page can become a gateway for SQL injection.

How the Exploit Works

Normally, schoolname is just the name of the school, e.g., “Lincoln High School.” But what if an attacker can edit that value (e.g., via some admin panel vulnerability or direct database access) to be malicious SQL? Then—instead of merely displaying the name—the code may accidentally execute injected SQL commands.

Suppose the attacker manages to set the schoolname column to

Lincoln High School' UNION SELECT password FROM users WHERE 'a'='a

Or use a payload to show the first user's password

Lincoln High School' UNION SELECT password FROM users LIMIT 1;--

When the code runs the following SQL

SELECT schoolname FROM schoolinfo

The injected row manipulates the output. If not properly filtered, mysql_fetch_array($result) may pull an extra row with the password from the users table, exposing it on the page.

Remote Injection

If there's any web form or URL parameter that allows users to update the school name, an attacker could exploit the vulnerability directly through the web interface, without database access.

Example attacker input in web form

Lincoln High School'; DROP TABLE students; --

If the input isn’t properly escaped or filtered, and is later echoed or used in further queries, this could cause destructive SQL commands to run, like dropping a table.

Stolen information appears in header or source.

Or, if used in a query that fetches user data — payload could escalate to authentication bypass, depending on how it's later used.

Escape Output: Always use htmlspecialchars() when echoing user-supplied data.

2. Use Prepared Statements: Replace mysql_query with PDO or MySQLi and never embed variables directly in SQL.

Example Secure Code

echo "<h1>" . htmlspecialchars($schoolname, ENT_QUOTES, 'UTF-8') . "</h1>";

And for secure database queries, use prepared statements.

References

- NVD Entry for CVE-2023-40944
- Schoolmate GitHub
- OWASP SQL Injection Guide

Summary

CVE-2023-40944 highlights the danger of trusting unsanitized data—even data you think is safe in the database. If you use Schoolmate 1.3, update, patch, or patch the code to escape and sanitize all database outputs. As always, regular code and security audits help keep your school's data safe.

Timeline

Published on: 09/11/2023 20:15:10 UTC
Last modified on: 09/13/2023 03:49:47 UTC