Improper input validation in Symfony - CVE-2018-19789

Detailed vulnerability description

The vulnerability allows a remote attacker to execute arbitrary code on the target system.

The vulnerability exists due to an error when using the scalar type hint `string` in a setter method (e.g. `setName(string $name)`) of a class that's the `data_class` of a form A remote unauthenticated attacker can submit a file upload to the corresponding field instead of a normal text input, call `UploadedFile::__toString()` which will then return and disclose the path of the uploaded file. If combined with a local file inclusion issue in certain circumstances a remote attacker can execute arbitrary code with elevated privileges.

Successful exploitation of this vulnerability may result in complete compromise of vulnerable system.

How to mitigate CVE-2018-19789

Sources

• https://symfony.com/blog/cve-2018-19789-disclosure-of-uploaded-files-full-path