Package Instance

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.

Remote code execution in PHPMailer
### Impact
The `mailSend` function in the default `isMail` transport in PHPMailer before 5.2.18 might allow remote attackers to pass extra parameters to the mail command and consequently execute arbitrary code via a \" (backslash double quote) in a crafted `Sender` property.

### Patches
Fixed in 5.2.18

### Workarounds
Filter and validate user input before passing it to internal functions.

### References
https://nvd.nist.gov/vuln/detail/CVE-2016-10033
Related to a follow-on issue in https://nvd.nist.gov/vuln/detail/CVE-2016-10045

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

Object injection
PHPMailer is vulnerable to an object injection attack.

Local File Disclosure
PHPMailer's `msgHTML` method applies transformations to an HTML document to make it usable as an email message body. One of the transformations is to convert relative image URLs into attachments using a script-provided base directory. If no base directory is provided, it resolves to `/`, meaning that relative image URLs get treated as absolute local file paths and added as attachments.