Improper Control of Generation of Code ('Code Injection')
Composer is a dependency manager for PHP. URLs for Mercurial repositories in the root composer.json and package source download URLs are not sanitized correctly. Specifically crafted URL values allow code to be executed in the HgDriver if hg/Mercurial is installed on the system. The impact to Composer users directly is limited as the composer.json file is typically under their own control and source download URLs can only be supplied by third party Composer repositories they explicitly trust to download and execute source code from, e.g. Composer plugins. The main impact is to services passing user input to Composer, including Packagist.org and Private Packagist. This allowed users to trigger remote code execution. The vulnerability has been patched on Packagist.org and Private Packagist within 12h of receiving the initial vulnerability report and based on a review of logs, to the best of our knowledge, was not abused by anyone. Other services/tools using VcsRepository/VcsDriver or derivatives may also be vulnerable and should upgrade their composer/composer dependency immediately. Versions 1.10.22 and 2.0.13 include patches for this issue.
CWE-94 - Code Injection
Code injection is a type of vulnerability that allows an attacker to execute arbitrary code. This vulnerability fully compromises the machine and can cause a wide variety of security issues, such as unauthorized access to sensitive information, manipulation of data, denial of service attacks etc. Code injection is different from command injection in the fact that it is limited by the functionality of the injected language (e.g. PHP), as opposed to command injection, which leverages existing code to execute commands, usually within the context of a shell.