Vulnerability record

CVE-2016-10033

PHPMailer Command Injection Vulnerability

CriticalExploitation confirmedCISA KEV

What should I do?

This vulnerability is in the CISA Known Exploited Vulnerabilities catalog: attackers are using it. If you run PHPMailer, fix it now.

CISA required action: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

US federal civilian agencies must remediate by Jul 28, 2025.

Patch status

Official fix available since Sep 30, 2026

Apply the vendor's update to every affected system. Check the fixed-in versions below where known.

Basis: NVD patch reference

Description

The mailSend function in the isMail transport in PHPMailer before 5.2.18 might allow remote attackers to pass extra parameters to the mail command and consequently execute arbitrary code via a \" (backslash double quote) in a crafted Sender property.

Source: NIST National Vulnerability Database. Official vulnerability data, reproduced as published.

Affected products

Products affected by this vulnerability, with versions and the source of each entry
Product	Vendor	Affected versions	Source
Joomla!	Joomla!	>= 1.5.0, <= 3.6.5	NVD
PHPMailer	PHP	—	KEV
WordPress	WordPress	<= 4.7	NVD

Sources: NVD = NIST National Vulnerability Database; KEV = CISA Known Exploited Vulnerabilities catalog.

Intelligence timeline

Developments from the last 30 days, newest first.

CVSS scoredUpdateKEVSep 30, 2026
CVE-2016-10033 scored CVSS 9.8: PHP PHPMailer, PHPMailer Command Injection Vulnerability
CISA lists this as exploited in the wild. Unpatched PHPMailer systems are exposed to active attacks now.
Basis: NIST National Vulnerability Database
Patch releasedUpdateKEVSep 30, 2026
Patch released for CVE-2016-10033: PHP PHPMailer, PHPMailer Command Injection Vulnerability
An official fix is now available for PHP PHPMailer. This vulnerability is being exploited, so apply it promptly.
Basis: NVD patch reference

1 earlier event is available with a subscription. See plans.

Coverage

We have not published a story about this vulnerability yet.

References

github.com https://github.com/PHPMailer/PHPMailer/releases/tag/v5.2.18
github.com https://github.com/advisories/GHSA-5f37-gxvh-23v6
nvd.nist.gov https://nvd.nist.gov/vuln/detail/CVE-2016-10033
packetstormsecurity.com http://packetstormsecurity.com/files/140291/PHPMailer-Remote-Code-Execution.html
packetstormsecurity.com http://packetstormsecurity.com/files/140350/PHPMailer-Sendmail-Argument-Injection.html
seclists.org http://seclists.org/fulldisclosure/2016/Dec/78
rapid7.com http://www.rapid7.com/db/modules/exploit/multi/http/phpmailer_arg_injection
securityfocus.com http://www.securityfocus.com/archive/1/539963/100/0/threaded
securityfocus.com http://www.securityfocus.com/bid/95108
securitytracker.com http://www.securitytracker.com/id/1037533
developer.joomla.org https://developer.joomla.org/security-centre/668-20161205-phpmailer-security-advisory.html
github.com https://github.com/PHPMailer/PHPMailer/wiki/About-the-CVE-2016-10033-and-CVE-2016-10045-vulnerabilities
legalhackers.com https://legalhackers.com/advisories/PHPMailer-Exploit-Remote-Code-Exec-CVE-2016-10033-Vuln.html
drupal.org https://www.drupal.org/psa-2016-004
exploit-db.com https://www.exploit-db.com/exploits/40968/
exploit-db.com https://www.exploit-db.com/exploits/40969/
exploit-db.com https://www.exploit-db.com/exploits/40970/
exploit-db.com https://www.exploit-db.com/exploits/40974/
exploit-db.com https://www.exploit-db.com/exploits/40986/
exploit-db.com https://www.exploit-db.com/exploits/41962/
exploit-db.com https://www.exploit-db.com/exploits/41996/
exploit-db.com https://www.exploit-db.com/exploits/42024/
exploit-db.com https://www.exploit-db.com/exploits/42221/
cisa.gov https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2016-10033