CVE-2021-3603: Fedoraproject Fedora

High severity, CVSS 8.1. EPSS: 2.3% chance of exploitation in the next 30 days.

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.

Affected products

• Fedoraproject Fedora: version 33 only; version 34 only
• PHPMailer Project PHPMailer: up to and including 6.4.1

Published 2021-06-17. Last modified 2026-06-17.