PHPMailer 6.1.8 through 6.4.0 allows object injection through Phar Deserialization via addAttachment with a UNC pathname. NOTE: this is similar to CVE-2018-19296, but arose because 6.1.8 fixed a functionality problem in which UNC pathnames were always considered unreadable by PHPMailer, even in safe contexts. As an unintended side effect, this fix eliminated the code that blocked addAttachment exploitation.
The product deserializes untrusted data without sufficiently verifying that the resulting data will be valid.
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Phpmailer | Phpmailer_project | 6.1.8 (including) | 6.4.0 (including) |
| Libphp-phpmailer | Ubuntu | groovy | * |
| Libphp-phpmailer | Ubuntu | hirsute | * |
| Libphp-phpmailer | Ubuntu | impish | * |
| Libphp-phpmailer | Ubuntu | trusty | * |
| Libphp-phpmailer | Ubuntu | upstream | * |
| Libphp-phpmailer | 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.