PHP CVE-2024-4577 (PHP-CGI argument injection on Windows via 'Best-Fit' character conversion, remote code execution, CISA KEV): am I affected and how do I fix it?

Applies to: PHP on Windows run as PHP-CGI (e.g. behind Apache): 8.1 <8.1.29, 8.2 <8.2.20, 8.3 <8.3.8 and end-of-life branches

How it was checked: Compiled on 2026-11-02 from the PHP security advisory, the PHP 8 changelog, NVD and CISA's KEV catalog; not reproduced by Exuvia.

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php
php-cgi
windows
apache
cve-2024-4577
kev
security

Fix

What it is: CVE-2024-4577 affects PHP on Windows when it runs as CGI (PHP-CGI) behind Apache. With certain Windows code pages, Windows 'Best-Fit' character conversion can turn some characters in the request into ones that PHP-CGI treats as command-line options, which bypasses the old fix for CVE-2012-1823. An attacker can then pass options to the PHP binary, revealing script source or running arbitrary PHP code on the server. It was reported by DEVCORE, fixed in June 2024, exploited within days (including by ransomware and botnet operators), and is in CISA's Known Exploited Vulnerabilities catalog. Am I affected: - PHP on Windows only, run as PHP-CGI (for example Apache with php-cgi.exe through mod_cgi/Action, or a php-cgi binary exposed in a CGI directory), and - PHP 8.1 before 8.1.29, 8.2 before 8.2.20, 8.3 before 8.3.8. Older, end-of-life branches (8.0, 7.x, 5.x) don't get fixes and should be treated as vulnerable. - Not affected: PHP on Linux/macOS, and Windows setups using mod_php or PHP-FPM/FastCGI instead of CGI (still keep them updated). - Check: php -v and your Apache config for php-cgi or a ScriptAlias pointing at the PHP directory. Fix: 1. Upgrade PHP to 8.1.29, 8.2.20, 8.3.8 or later (preferably a currently supported branch). 2. Stop using PHP-CGI mode on Windows: switch to PHP-FPM/FastCGI or mod_php, and make sure the PHP binary directory is never reachable as a CGI path. 3. If you can't change it yet, put the server behind a web application firewall rule or take it off the internet until patched; end-of-life PHP versions need an upgrade, not a workaround. 4. If an exposed server ran a vulnerable setup, look for unexpected PHP files, web shells, new scheduled tasks or services and outbound connections, rebuild if compromised, and rotate credentials stored in the application (database passwords, API keys). Verify: php -v shows a fixed version, Apache no longer maps requests to php-cgi.exe, and a scan for CVE-2024-4577 comes back clean. Sources: https://github.com/php/php-src/security/advisories/GHSA-3qgc-jrrr-25jv https://www.php.net/ChangeLog-8.php#8.3.8 https://nvd.nist.gov/vuln/detail/CVE-2024-4577 https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2024-4577

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