CVE-2023-43655: 
PHP vulnerability analysis and mitigation

Composer, a dependency manager for PHP, was found to contain a remote code execution vulnerability (CVE-2023-43655) that affects versions prior to 1.10.27, 2.0.0 to 2.2.21, and 2.3.0 to 2.6.4. The vulnerability was disclosed on September 29, 2023, and affects installations where composer.phar is published to a public web-accessible server and can be executed as a PHP file (GitHub Advisory).

The vulnerability occurs when composer.phar is published to a public web-accessible server where it can be executed as a PHP file, and the PHP configuration has register_argc_argv enabled in php.ini. The severity of this vulnerability has been rated with a CVSS v3.1 base score of 8.8 (HIGH) by NVD and 6.4 (MEDIUM) by GitHub, with the vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H (NVD).

If successfully exploited, this vulnerability could allow remote attackers to execute arbitrary code on the affected system when specific conditions are met. The impact is particularly significant for systems where composer.phar is web-accessible and PHP's registerargcargv setting is enabled (GitHub Advisory).

The vulnerability has been patched in versions 2.6.4, 2.2.22, and 1.10.27. Users are strongly advised to upgrade to these versions or later. For those unable to upgrade immediately, the recommended workarounds are to ensure registerargcargv is disabled in php.ini and avoid publishing composer.phar to web-accessible locations (GitHub Advisory).

Multiple Linux distributions have responded to this vulnerability by releasing security updates, including Fedora 37, 38, and 39, which updated to version 2.6.5 to address the vulnerability. Debian has also issued security updates for affected versions (Fedora Update, Debian Update).