PHP · PHPMailer
CVE-2016-10033
PHPMailer Command Injection Vulnerability
What it is
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.
CISA: PHPMailer contains a command injection vulnerability because it fails to sanitize user-supplied input. Specifically, this issue affects the 'mail()' function of 'class.phpmailer.php' script. An attacker can exploit this issue to execute arbitrary code within the context of the application. Failed exploit attempts will result in a denial-of-service condition.
What to do
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Deadline for US federal agencies: July 28, 2025
- Added to the CISA list
- July 7, 2025
- Published
- December 30, 2016
- Severity
- Critical 9.8 CVSS 3.1
- Chance of attacks in the next 30 days (EPSS)
- 99.7% in the top 0.1% of all known vulnerabilities
- Weakness
- CWE-77 CWE-88
- More details
- NVD · CVE.org · CISA
All references (20)
- http://packetstormsecurity.com/files/140350/PHPMailer-Sendmail-Argument-Injection.html
- https://www.drupal.org/psa-2016-004
- https://www.exploit-db.com/exploits/42221/
- https://www.exploit-db.com/exploits/40969/
- https://www.exploit-db.com/exploits/41962/
- https://www.exploit-db.com/exploits/40968/
- https://legalhackers.com/advisories/PHPMailer-Exploit-Remote-Code-Exec-CVE-2016-10033-Vuln.html
- https://github.com/PHPMailer/PHPMailer/releases/tag/v5.2.18
- http://www.securityfocus.com/archive/1/539963/100/0/threaded
- https://github.com/PHPMailer/PHPMailer/wiki/About-the-CVE-2016-10033-and-CVE-2016-10045-vulnerabilities
- http://packetstormsecurity.com/files/140291/PHPMailer-Remote-Code-Execution.html
- https://www.exploit-db.com/exploits/40974/
- https://www.exploit-db.com/exploits/40986/
- https://www.exploit-db.com/exploits/40970/
- http://www.rapid7.com/db/modules/exploit/multi/http/phpmailer_arg_injection
- https://www.exploit-db.com/exploits/41996/
- http://seclists.org/fulldisclosure/2016/Dec/78
- http://www.securityfocus.com/bid/95108
- http://www.securitytracker.com/id/1037533
- https://developer.joomla.org/security-centre/668-20161205-phpmailer-security-advisory.html
More exploited flaws from PHP
| Added | Vulnerability | Product | Severity | Attack chance |
|---|---|---|---|---|
| Mar 25, 2022 | PHP-CGI Query String Parameter | PHP | Critical 9.8 | >99.9% |
| Mar 25, 2022 | Buffer Overflow | FastCGI Process Manager (FPM) | High 8.7 | 99.7% |
Sources: Known Exploited Vulnerabilities (CISA, public domain), CVE records (cve.org) and EPSS (FIRST). The chance of attacks is the EPSS estimate that someone will try to exploit the flaw in the next 30 days.