DomPDF before version 2.0.0 is vulnerable to PHAR deserialization due to a lack of checking on the protocol before passing it into the file_get_contents() function. An attacker who can upload files of any type to the server 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 DOMPdf is used with frameworks with documented POP chains like Laravel or vulnerable developer code.
The product deserializes untrusted data without sufficiently verifying that the resulting data will be valid.
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Dompdf | Dompdf_project | * | 2.0.0 (excluding) |
| Php-dompdf | Ubuntu | bionic | * |
| Php-dompdf | Ubuntu | esm-apps/bionic | * |
| Php-dompdf | Ubuntu | esm-apps/xenial | * |
| Php-dompdf | Ubuntu | focal | * |
| Php-dompdf | Ubuntu | jammy | * |
| Php-dompdf | Ubuntu | kinetic | * |
| Php-dompdf | Ubuntu | trusty | * |
| Php-dompdf | Ubuntu | upstream | * |
| Php-dompdf | Ubuntu | xenial | * |
It is often convenient to serialize objects for communication or to save them for later use. However, deserialized data or code can often be modified without using the provided accessor functions if it does not use cryptography to protect itself. Furthermore, any cryptography would still be client-side security – which is a dangerous security assumption. Data that is untrusted can not be trusted to be well-formed. When developers place no restrictions on “gadget chains,” or series of instances and method invocations that can self-execute during the deserialization process (i.e., before the object is returned to the caller), it is sometimes possible for attackers to leverage them to perform unauthorized actions, like generating a shell.