Package Instance

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).

Insufficient output escaping of attachment names in PHPMailer
### Impact
CWE-116: Incorrect output escaping.

An attachment added like this (note the double quote within the attachment name, which is entirely valid):

    $mail->addAttachment('/tmp/attachment.tmp', 'filename.html";.jpg');

Will result in a message containing these headers:

    Content-Type: application/octet-stream; name="filename.html";.jpg"
    Content-Disposition: attachment; filename="filename.html";.jpg"

The attachment will be named `filename.html`, and the trailing `";.jpg"` will be ignored. Mail filters that reject `.html` attachments but permit `.jpg` attachments may be fooled by this.

Note that the MIME type itself is obtained automatically from the *source filename* (in this case `attachment.tmp`, which maps to a generic `application/octet-stream` type), and not the *name* given to the attachment (though these are the same if a separate name is not provided), though it can be set explicitly in other parameters to attachment methods.

### Patches
Patched in PHPMailer 6.1.6 by escaping double quotes within the name using a backslash, as per RFC822 section 3.4.1, resulting in correctly escaped headers like this:

    Content-Type: application/octet-stream; name="filename.html\";.jpg"
    Content-Disposition: attachment; filename="filename.html\";.jpg"

### Workarounds
Reject or filter names and filenames containing double quote (`"`) characters before passing them to attachment functions such as `addAttachment()`.

### References
[CVE-2020-13625](https://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2020-13625).
[PHPMailer 6.1.6 release](https://github.com/PHPMailer/PHPMailer/releases/tag/v6.1.6)

### For more information
If you have any questions or comments about this advisory:
* Open an issue in [the PHPMailer repo](https://github.com/PHPMailer/PHPMailer/issues)

Object injection in PHPMailer/PHPMailer
### Impact
This is a reintroduction of an earlier issue (CVE-2018-19296) by an unrelated bug fix in PHPMailer 6.1.8.  An external file may be unexpectedly executable if it is used as a path to an attachment file via PHP's support for `.phar` files`. Exploitation requires that an attacker is able to provide an unfiltered path to a file to attach, or to trick calling code into generating one. See [this article](https://knasmueller.net/5-answers-about-php-phar-exploitation) for more info.

### Patches
This issue was patched in the PHPMailer 6.4.1 release. This release also implements stricter filtering for attachment paths; paths that look like *any* kind of URL are rejected.

### Workarounds
Validate paths to loaded files using the same pattern as used in [`isPermittedPath()`](https://github.com/PHPMailer/PHPMailer/blob/master/src/PHPMailer.php#L1815) before using them in *any* PHP file function, such as `file_exists`. This method can't be used directly because it is protected, but you can implement the same thing in calling code. Note that this should be applied to *all* user-supplied paths passed into such functions; it's not a problem specific to PHPMailer.

### Credit
This issue was found by Fariskhi Vidyan, reported and managed via Tidelift.