PHAR deserialization allowing remote code execution
Descriptionsnappy is vulnerable to PHAR deserialization due to a lack of checking on the protocol before passing it into the `file_exists()` function. If an attacker can upload files of any type to the server he can pass in the phar:// protocol to unserialize the uploaded file and instantiate arbitrary PHP objects. This can lead to remote code execution especially when snappy is used with frameworks with documented POP chains like Laravel/Symfony vulnerable developer code. If user can control the output file from the `generateFromHtml()` function, it will invoke deserialization.Proof of ConceptInstall Snappy via composer require `knplabs/knp-snappy`. After that, under snappy directory, create an `index.php` file with this vulnerable code.As an attacker, we going to generate the malicious phar using this script.Then run these command to generate the fileThen execute index.php with `php index.php`. You will see a file named `pwned` will be created. Noted that attacker can upload a file with any extension such as .png or .jpeg. So poc.jpeg also will do the trick.ImpactThis vulnerability is capable of remote code execution if Snappy is used with frameworks or developer code with vulnerable POP chains.Occurences<https://github.com/KnpLabs/snappy/blob/5126fb5b335ec929a226314d40cd8dad497c3d67/src/Knp/Snappy/AbstractGenerator.php#L670>References<https://huntr.dev/bounties/0bdddc12-ff67-4815-ab9f-6011a974f48e/>