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.
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"
Reject or filter names and filenames containing double quote ("
) characters before passing them to attachment functions such as addAttachment()
.
CVE-2020-13625.
PHPMailer 6.1.6 release
If you have any questions or comments about this advisory:
lists.opensuse.org/opensuse-security-announce/2020-07/msg00067.html
lists.opensuse.org/opensuse-security-announce/2020-07/msg00085.html
github.com/PHPMailer/PHPMailer
github.com/PHPMailer/PHPMailer/commit/c2796cb1cb99d7717290b48c4e6f32cb6c60b7b3
github.com/PHPMailer/PHPMailer/releases/tag/v6.1.6
github.com/PHPMailer/PHPMailer/security/advisories/GHSA-f7hx-fqxw-rvvj
lists.debian.org/debian-lts-announce/2020/06/msg00014.html
lists.debian.org/debian-lts-announce/2020/08/msg00004.html
lists.fedoraproject.org/archives/list/[email protected]/message/EFM3BZABL6RUHTVMXSC7OFMP4CKWMRPJ
lists.fedoraproject.org/archives/list/[email protected]/message/SMH4TC5XTS3KZVGMSKEPPBZ2XTZCKKCX
nvd.nist.gov/vuln/detail/CVE-2020-13625
usn.ubuntu.com/4505-1