CVE-2021-3603
8.1 · HIGHOverview
CVE-2021-3603 is a high-severity vulnerability affecting phpmailer_project phpmailer. It was published on June 17, 2021 and has a CVSS 3.1 base score of 8.1 (HIGH).
This vulnerability has a CVSS 3.1 base score of 8.1, rated HIGH. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.
Technical Description
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.
Remediation
Check the references section for vendor advisories and patches from phpmailer_project. Update phpmailer to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
Affected Products
| Vendor | Product | Versions | Status |
|---|---|---|---|
| phpmailer_project | phpmailer | 0 | Affected |
References
Frequently Asked Questions
What is CVE-2021-3603?
CVE-2021-3603 is a high-severity vulnerability affecting phpmailer_project phpmailer. It was published on June 17, 2021 and has a CVSS 3.1 base score of 8.1 (HIGH).
How severe is CVE-2021-3603?
This vulnerability has a CVSS 3.1 base score of 8.1, rated HIGH. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.
How do I fix or remediate CVE-2021-3603?
Check the references section for vendor advisories and patches from phpmailer_project. Update phpmailer to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
How can CyberStrike help with CVE-2021-3603?
CyberStrike's AI-powered security agents can automatically detect CVE-2021-3603 across your infrastructure using autonomous pentesting, DAST scanning, and HackBrowser. The platform continuously monitors for known vulnerabilities and provides actionable remediation guidance prioritized by real-world exploitability.
How CyberStrike Helps
AI agents map your attack surface to find vulnerabilities like this one.
Automated penetration testing that runs continuously, not just quarterly.
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