CVE-2020-13625

PHPMailer before 6.1.6 contains an output escaping bug when the name of a file attachment contains a double quote character. This can result in the file type being misinterpreted by the receiver or any mail relay processing the message.

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

PHPMailer before 6.1.6 contains an output escaping bug when the name of a file attachment contains a double quote character. This can result in the file type being misinterpreted by the receiver or any mail relay processing the message.

PHPMailer before 6.1.6 contains an output escaping bug when the name of a file attachment contains a double quote character. This can result in the file type being misinterpreted by the receiver or any mail relay processing the message.

TuxCare rebuilt phpmailer/phpmailer to address 3 CVEs. Fixed in 5.2.28-p1+tuxcare.

Fix insufficient output escaping bug in file attachment names (CVE-2020-13625).

This update for cacti, cacti-spine fixes the following issues:

• cacti 1.2.13:

  • Query XSS vulnerabilities require vendor package update (CVE-2020-11022 / CVE-2020-11023)
  • Lack of escaping on some pages can lead to XSS exposure
  • Update PHPMailer to 6.1.6 (CVE-2020-13625)
  • SQL Injection vulnerability due to input validation failure when editing colors (CVE-2020-14295, boo#1173090)
  • Lack of escaping on template import can lead to XSS exposure

• switch from cron to systemd timers (boo#1115436):

  • cacti-cron.timer
  • cacti-cron.service

• avoid potential root escalation on systems with fs.protected_hardlinks=0 (boo#1154087): handle directory permissions in file section instead of using chown during post installation

• rewrote apache configuration to get rid of .htaccess files and explicitely disable directory permissions per default (only allow a limited, well-known set of directories)

This update for cacti, cacti-spine fixes the following issues:

• cacti 1.2.13:

  • Query XSS vulnerabilities require vendor package update (CVE-2020-11022 / CVE-2020-11023)
  • Lack of escaping on some pages can lead to XSS exposure
  • Update PHPMailer to 6.1.6 (CVE-2020-13625)
  • SQL Injection vulnerability due to input validation failure when editing colors (CVE-2020-14295, boo#1173090)
  • Lack of escaping on template import can lead to XSS exposure

• switch from cron to systemd timers (boo#1115436):

  • cacti-cron.timer
  • cacti-cron.service

• avoid potential root escalation on systems with fs.protected_hardlinks=0 (boo#1154087): handle directory permissions in file section instead of using chown during post installation

• rewrote apache configuration to get rid of .htaccess files and explicitely disable directory permissions per default (only allow a limited, well-known set of directories)

This update was imported from the openSUSE:Leap:15.1:Update update project.

These are all security issues fixed in the cacti-1.2.18-1.2 package on the GA media of openSUSE Tumbleweed.

Elar Lang discovered that PHPMailer did not properly escape double quote characters in filenames. A remote attacker could possibly exploit this with a crafted filename to bypass attachment filters that are based on matching filename extensions. (CVE-2020-13625)

Dawid Golunski discovered that PHPMailer was not properly escaping user input data used as arguments to functions executed by the system shell. An attacker could possibly use this issue to execute arbitrary code. This issue only affected Ubuntu 16.04 ESM. (CVE-2016-10033, CVE-2016-10045)

It was discovered that PHPMailer was not properly escaping characters in certain fields of the code_generator.php example code. An attacker could possibly use this issue to conduct cross-site scripting (XSS) attacks. This issue was only fixed in Ubuntu 16.04 ESM and Ubuntu 18.04 ESM. (CVE-2017-11503)

Yongxiang Li discovered that PHPMailer was not properly converting relative paths provided as user input when adding attachments to messages, which could lead to relative image URLs being treated as absolute local file paths and added as attachments. An attacker could possibly use this issue to access unauthorized resources and expose sensitive information. This issue only affected Ubuntu 16.04 ESM. (CVE-2017-5223)

Sehun Oh discovered that PHPMailer was not properly processing untrusted non-local file attachments, which could lead to an object injection. An attacker could possibly use this issue to execute arbitrary code. This issue only affected Ubuntu 16.04 ESM. (CVE-2018-19296)

Elar Lang discovered that PHPMailer was not properly escaping file attachment names, which could lead to a misinterpretation of file types by entities processing the message. An attacker could possibly use this issue to bypass attachment filters. This issue was only fixed in Ubuntu 16.04 ESM and Ubuntu 20.04 ESM. (CVE-2020-13625)

It was discovered that PHPMailer was not properly handling callables in its validateAddress function, which could result in untrusted code being called should the global namespace contain a function called 'php'. An attacker could possibly use this issue to execute arbitrary code. This issue was only fixed in Ubuntu 20.04 ESM and Ubuntu 22.04 ESM. (CVE-2021-3603)