CVE-2024-4577: PHP CGI on Windows RCE Vulnerability

CVE-2024-4577 Overview

In PHP versions 8.1.* before 8.1.29, 8.2.* before 8.2.20, 8.3.* before 8.3.8, when using Apache and PHP-CGI on Windows, if the system is set up to use certain code pages, Windows may use "Best-Fit" behavior to replace characters in command line given to Win32 API functions. PHP CGI module may misinterpret those characters as PHP options, which may allow a malicious user to pass options to PHP binary being run, and thus reveal the source code of scripts, run arbitrary PHP code on the server, etc.

Critical Impact
PHP-CGI module misinterpretation may lead to unauthorized command execution and code exposure.

Affected Products

php php
microsoft windows
fedoraproject fedora

Discovery Timeline

Not Available - Vulnerability discovered by Not Available
Not Available - Responsible disclosure to php
Not Available - CVE CVE-2024-4577 assigned
Not Available - php releases security patch
2024-06-09 - CVE CVE-2024-4577 published to NVD
2025-11-03 - Last updated in NVD database

Technical Details for CVE-2024-4577

Vulnerability Analysis

The vulnerability lies in the PHP CGI mode on Windows when configured to use specific code pages. This results in improper character interpretation by the Win32 API, which can be exploited by attackers to execute arbitrary PHP code or expose source code by passing unintended options to the PHP binary.

Root Cause

The root cause of the vulnerability is the "Best-Fit" mapping behavior in the Windows Win32 API that leads to misinterpretation of command-line arguments in PHP-CGI.

Attack Vector

The attack vector for this vulnerability is the network, allowing remote attackers to exploit the vulnerability by sending crafted requests.

php

// Example exploitation code (sanitized)
<?php
ini_set('user_ini.filename', '/path/to/malicious/script.php');
// Further malicious actions
?>

Detection Methods for CVE-2024-4577

Indicators of Compromise

Unauthorized PHP code execution
Unexpected PHP error logs indicating misinterpretation of CGI parameters
Unusual traffic patterns targeting PHP-CGI instances

Detection Strategies

Monitoring PHP error logs for anomalies and unrecognized options or parameters can help in early identification. Network traffic analysis may reveal unusual request patterns exploiting this vulnerability.

Monitoring Recommendations

Implement logging for 400 and 500 HTTP status codes and monitor for deviations in traffic to PHP-CGI endpoints. Using SentinelOne’s runtime behavior analysis helps detect unexpected PHP process behaviors indicative of exploitation.

How to Mitigate CVE-2024-4577

Immediate Actions Required

Disable "Best-Fit" mapping in the Windows configuration
Restrict access to PHP binaries
Immediately apply available patches from PHP

Patch Information

Patches are available as part of updates to PHP 8.1.29, 8.2.20, and 8.3.8. Refer to the PHP ChangeLog for more information.

Workarounds

As a workaround, consider using alternative configurations that do not rely on problematic code pages or "Best-Fit" mapping behavior.

bash

# Configuration example to secure cgi-bin
<Directory "C:/path/to/cgi-bin">
    Options -Indexes +ExecCGI
    AllowOverride None
    Require all granted
</Directory>