Remote Code Execution vulnerability in PHPMailer 6.4.1 running on Windows
PHPMailer 6.4.1 contains a possible remote code execution vulnerability through the $lang_path parameter of the setLanguage() method. If the $lang_path parameter is passed unfiltered from user input, it can be set to a UNC path, and if an attacker is also able to create a remote mount on the server that the UNC path points to, a script file under their control may be executed.
Impact
Arbitrary code may be run by a remote attacker under the web server or PHP process running on Window hosts.
Patches
Mitigated in PHPMailer 6.5.0 by no longer treating translation files as PHP code, but by parsing their text content directly. This approach avoids the possibility of executing unknown code while retaining backward compatibility. This isn't ideal, so the current translation format is deprecated and will be replaced in the next major release.
Workarounds
Any of:
- Ensure that calling code does not pass unfiltered user-supplied data to the
$lang_pathparameter of thesetLanguage()method. - Block or filter the use of unknown UNC paths in this parameter (or altogether).
- Ensure that unauthorised users do not have the ability to read from unknown remote servers via UNC paths.
- Run on an OS that does not support UNC paths
References
Reported by listensec.com via Tidelift.
For more information
If you have any questions or comments about this advisory:
- Open an issue in PHPMailer
- Email the maintainers
Affected software
Click a technology to see all vulnerabilities affecting it.
| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Composer package | phpmailer/phpmailer | < 6.5.0 | 6.5.0 |
References
- https://github.com/PHPMailer/PHPMailer/security/advisories/GHSA-7q44-r25x-wm4q
- https://nvd.nist.gov/vuln/detail/CVE-2021-34551
- https://github.com/PHPMailer/PHPMailer/commit/acd264bf17ff4ac5c915f0d4226dce8a9ea70bc3
- https://github.com/FriendsOfPHP/security-advisories/blob/master/phpmailer/phpmailer/CVE-2021-34551.yaml
- https://github.com/PHPMailer/PHPMailer/blob/master/SECURITY.md
- https://github.com/PHPMailer/PHPMailer/releases/tag/v6.5.0
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/3YRMWGA4VTMXFB22KICMB7YMFZNFV3EJ
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/FJYSOFCUBS67J3TKR74SD3C454N7VTYM
- CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H- Weakness (CWE)
CWE-434, CWE-94- Platform
- Composer
- Package
phpmailer/phpmailer- Disclosed
- 22.06.2021
- Updated
- 11.10.2026 10:22
Sources and licenses
OSV / GitHub Advisory Database - GHSA-7q44-r25x-wm4q - CC BY 4.0
Vulnerability history: phpmailer/phpmailer
All published vulnerabilities of this package (Composer package), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 13
- First → latest
- 12.2016 02.2024
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- Critical 2
- High 7
- Medium 3
- Low 1
Disclosures per year
- 2017: 0
- 2018: 0
- 2019: 0
- 2020: 5
- 2021: 3
- 2022: 2
- 2023: 0
- 2024: 2
- 2025: 0
- 2026: 0
earlier: 1
-
Remote Code Execution vulnerability in PHPMailer 6.4.1 running on Windows this entry
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