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GHSA-f7hx-fqxw-rvvj
No affected components available
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
The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a high impact on the integrity of the data.
Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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