The Composer method VcsDriver::getFileContent() with user-controlled $file or $identifier arguments is susceptible to an argument injection vulnerability. It can be leveraged to gain arbitrary command execution if the Mercurial or the Git driver are used.
This led to a vulnerability on Packagist.org and Private Packagist, i.e., using the composer.json readme field as a vector for injecting parameters into the $file argument for the Mercurial driver or via the $identifier argument for the Git and Mercurial drivers.
Composer itself can be attacked through branch names by anyone controlling a Git or Mercurial repository, which is explicitly listed by URL in a project's composer.json.
To the best of our knowledge, this was not actively exploited. The vulnerability has been patched on Packagist.org and Private Packagist within a day of the vulnerability report.
{
"github_reviewed_at": "2022-04-22T20:15:38Z",
"cwe_ids": [
"CWE-20",
"CWE-88",
"CWE-94"
],
"nvd_published_at": "2022-04-13T21:15:00Z",
"github_reviewed": true,
"severity": "HIGH"
}