Package Instance

Remote Code Execution vulnerability in PHPMailer 6.4.1 running on Windows
PHPMailer 6.4.1 contains a possible remote code execution vulnerability through the `$lang_path` parameter of the `setLanguage()` method. If the `$lang_path` parameter is passed unfiltered from user input, it can be set to [a UNC path](https://docs.microsoft.com/en-us/dotnet/standard/io/file-path-formats#unc-paths), and if an attacker is also able to create a remote mount on the server that the UNC path points to, a script file under their control may be executed. 

### Impact
Arbitrary code may be run by a remote attacker under the web server or PHP process running on Window hosts.

### Patches
Mitigated in PHPMailer 6.5.0 by no longer treating translation files as PHP code, but by parsing their text content directly.
This approach avoids the possibility of executing unknown code while retaining backward compatibility. This isn't ideal, so the current translation format is deprecated and will be replaced in the next major release.

### Workarounds
Any of:
* Ensure that calling code does not pass unfiltered user-supplied data to the `$lang_path` parameter of the `setLanguage()` method.
* Block or filter the use of unknown UNC paths in this parameter (or altogether).
* Ensure that unauthorised users do not have the ability to read from unknown remote servers via UNC paths.
* Run on an OS that does not support UNC paths

### References
[CVE-2021-34551](https://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2021-34551).

Reported by [listensec.com](https://listensec.com) via Tidelift.

### For more information
If you have any questions or comments about this advisory:
* Open an issue in [PHPMailer](https://github.com/PHPMailer/PHPMailer)
* [Email the maintainers](mailto:phpmailer@synchromedia.co.uk)

PHPMailer untrusted code may be run from an overridden address validator
If a function is defined that has the same name as the default built-in email address validation scheme (`php`), it will be called in default configuration as when no validation scheme is provided, the default scheme's callable `php` was being called. If an attacker is able to inject such a function into the application (a much bigger issue), it will be called whenever an email address is validated, such as when calling `validateAddress()`.

### Impact
Low impact – exploitation requires that an attacker can already inject code into an application, but it provides a trigger pathway.

### Patches
This is patched in PHPMailer 6.5.0 by denying the use of simple strings as validator function names, which is a very minor BC break.

### Workarounds
Inject your own email validator function.

### References
Reported by [Vikrant Singh Chauhan](mailto:vi@hackberry.xyz) via [huntr.dev](https://www.huntr.dev/).
[CVE-2021-3603](https://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2021-3603)

### For more information
If you have any questions or comments about this advisory:
* Open an issue in [the PHPMailer project](https://github.com/PHPMailer/PHPMailer)
* [Email us](mailto:phpmailer@synchromedia.co.uk).