An issue was discovered in Symfony 2.8.0 through 2.8.50, 3.4.0 through 3.4.34, 4.2.0 through 4.2.11, and 4.3.0 through 4.3.7. If an application passes unvalidated user input as the file for which MIME type validation should occur, then arbitrary arguments are passed to the underlying file command. This is related to symfony/http-foundation (and symfony/mime in 4.3.x).
https://symfony.com/blog/symfony-4-3-8-released
https://symfony.com/blog/cve-2019-18888-prevent-argument-injection-in-a-mimetypeguesser