zbateson/mail-mime-parser is a mail mime parser alternative to PHP's imap* functions and Pear libraries for reading messages in Internet Message Format RFC 822. Prior to version 3.0.6 and 4.0.2, CRLF (carriage-return / line-feed) header injection (CWE-93) affecting any application that uses this library to build or forward MIME messages with an attacker-influenced attachment filename. Attachment filenames are interpolated into the `Content-Type` and `Content-Disposition` header values without stripping CR/LF, so a filename containing `\r\n` serializes as one or more additional, attacker-controlled header lines (for example a forged `Bcc:` that silently exfiltrates a copy of the outgoing message). The untrusted filename can come directly from parsed inbound mail, so no local construction is required — an application that re-attaches or re-sends a parsed filename is exposed. Versions 3.0.6 and 4.0.2 patch the issue. Versions 1.x and 2.x are also affected but are end-of-life and will not receive patches; users on those lines should upgrade to a fixed release. If upgrading is not immediately possible, strip CR and LF from any filename before passing it to attachment APIs, and from the result of getFilename() before reusing it in a constructed message — e.g. preg_replace('/[\r\n]+/', ' ', $filename).

Affected: Packagist: zbateson/mail-mime-parser

### Impact

A CRLF (carriage-return / line-feed) header injection affecting any application that uses this library to build or forward MIME messages with an attacker-influenced attachment filename. Attachment filenames are interpolated into the `Content-Type` and `Content-Disposition` header values without stripping CR/LF, so a filename containing `\r\n` serializes as one or more additional, attacker-controlled header lines (for example a forged `Bcc:` that silently exfiltrates a copy of the outgoing message). The untrusted filename can come directly from parsed inbound mail, so no local construction is required — an application that re-attaches or re-sends a parsed filename is exposed.

### Details

On the outbound side, `MultipartHelper::createAndAddPartForAttachment()` sanitizes the filename only with `iconv('UTF-8','US-ASCII//translit//ignore', $filename)`. CR and LF are valid US-ASCII, so they survive that filter, and the value is then written into the header verbatim via `MimePart::setRawHeader()`. A filename of `doc\r\nBcc: attacker@evil.test` therefore serializes as:

``` Content-Disposition: attachment; filename="doc Bcc: attacker@evil.test" ```

The `filename` value closes after `doc`, and `Bcc: attacker@evil.test` stands as its own header line.

The decode side is affected as well, which is what makes purely inbound exploitation possible:

- `ParameterPart::decodePartValue()` `rawurldecode()`s an RFC 2231 `filename*=` parameter with no control-character strip…