CVE-2021-3603

If a function is defined that has the same name as the default built-in email address validation scheme (php), it will be called in default configuration as when no validation scheme is provided, the default scheme's callable php was being called. If an attacker is able to inject such a function into the application (a much bigger issue), it will be called whenever an email address is validated, such as when calling validateAddress().

Impact

Low impact – exploitation requires that an attacker can already inject code into an application, but it provides a trigger pathway.

Patches

This is patched in PHPMailer 6.5.0 by denying the use of simple strings as validator function names, which is a very minor BC break.

Workarounds

Inject your own email validator function.

References

Reported by Vikrant Singh Chauhan via huntr.dev. CVE-2021-3603

For more information

If you have any questions or comments about this advisory:

• Open an issue in the PHPMailer project
• Email us.

PHPMailer 6.4.1 and earlier contain a vulnerability that can result in untrusted code being called (if such code is injected into the host project's scope by other means). If the $patternselect parameter to validateAddress() is set to 'php' (the default, defined by PHPMailer::$validator), and the global namespace contains a function called php, it will be called in preference to the built-in validator of the same name. Mitigated in PHPMailer 6.5.0 by denying the use of simple strings as validator function names.

PHPMailer 6.4.1 and earlier contain a vulnerability that can result in untrusted code being called (if such code is injected into the host project's scope by other means). If the $patternselect parameter to validateAddress() is set to 'php' (the default, defined by PHPMailer::$validator), and the global namespace contains a function called php, it will be called in preference to the built-in validator of the same name. Mitigated in PHPMailer 6.5.0 by denying the use of simple strings as validator function names.

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

PHPMailer contained a vulnerability that can result in untrusted code being called (CVE-2021-3603).

See upstream release notes.

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)