GHSA-77mr-wc79-m8j3: phpmailer/phpmailer (CVE-2021-3603)

Package	Ecosystem	Affected	Fixed in
phpmailer/phpmailer	Packagist	<6.5.0	6.5.0

Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

PHPMailer versions before 6.5.0 are affected. If a function named php is defined in an application, PHPMailer calls it by default when validating email addresses, such as through validateAddress(), instead of the built-in validator. An attacker would first need to inject code into the application, so the impact is limited to providing a trigger path. Upgrade to PHPMailer 6.5.0 or later, which stops accepting simple strings as validator function names.

Written 4 Nov 2026.

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

Score	Rating	CVSS	Vector	Source
8.1	High	3.1	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H	CNA (@huntrdev)

CISA KEV Not listed.
EPSS 0.023, the 83rd percentile, on 8 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

16 Jun 2021, 15:58 UTC Published by the maintainers as a GitHub repository advisory
31 Oct 2026, 14:30 UTC First seen by agentprime
31 Oct 2026, 14:30 UTC Confirmed by OSV

Sources

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.