Ecosyste.ms: Advisories

Security Advisories: MDE2OlNlY3VyaXR5QWR2aXNvcnlHSFNBLWY3aHgtZnF4dy1ydnZq

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.
PHPMailer 6.1.6 release

For more information

If you have any questions or comments about this advisory:

• Open an issue in the PHPMailer repo

Permalink: https://github.com/advisories/GHSA-f7hx-fqxw-rvvj
JSON: https://advisories.ecosyste.ms/api/v1/advisories/MDE2OlNlY3VyaXR5QWR2aXNvcnlHSFNBLWY3aHgtZnF4dy1ydnZq
Source: GitHub Advisory Database
Origin: Unspecified
Severity: High
Classification: General
Published: almost 4 years ago
Updated: over 1 year ago

CVSS Score: 7.5
CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

Identifiers: GHSA-f7hx-fqxw-rvvj, CVE-2020-13625
References:

• https://github.com/PHPMailer/PHPMailer/security/advisories/GHSA-f7hx-fqxw-rvvj
• https://github.com/PHPMailer/PHPMailer/commit/c2796cb1cb99d7717290b48c4e6f32cb6c60b7b3
• https://github.com/PHPMailer/PHPMailer/releases/tag/v6.1.6
• https://nvd.nist.gov/vuln/detail/CVE-2020-13625
• https://lists.debian.org/debian-lts-announce/2020/06/msg00014.html
• https://lists.fedoraproject.org/archives/list/[email protected]/message/SMH4TC5XTS3KZVGMSKEPPBZ2XTZCKKCX/
• https://lists.fedoraproject.org/archives/list/[email protected]/message/EFM3BZABL6RUHTVMXSC7OFMP4CKWMRPJ/
• http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00067.html
• http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00085.html
• https://lists.debian.org/debian-lts-announce/2020/08/msg00004.html
• https://usn.ubuntu.com/4505-1/
• https://github.com/advisories/GHSA-f7hx-fqxw-rvvj

Repository: https://github.com/PHPMailer/PHPMailer
Blast Radius: 32.1

Affected Packages