GHSA-77mr-wc79-m8j3
HIGHPHPMailer untrusted code may be run from an overridden address validator
Blast Radius
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Description
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | phpmailer/phpmailer | all versions | 6.5.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for phpmailer/phpmailer. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update phpmailer/phpmailer to 6.5.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-77mr-wc79-m8j3 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-77mr-wc79-m8j3 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-77mr-wc79-m8j3. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-77mr-wc79-m8j3 in your dependencies?
O3 detects GHSA-77mr-wc79-m8j3 across Packagist dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.