CVE-2016-10033 PHP PHPMailer: command or code injection
In plain words: The program treats text it receives as instructions instead of plain data. The attacker can run commands on the machine — often the whole device is taken over.
Confirmed exploited by CISA on · US federal patch deadline Jul 28, 2025
What to do
- Install PHP's security update for PHPMailer. If no update exists, follow the vendor's workaround or stop using the product until one ships.
- Keep a list of every internet-facing server you run so nothing is forgotten.
- Patch anything in this catalog first, ahead of normal patch cycles.
- Put admin and file-transfer apps behind a VPN or single sign-on instead of the open internet.
Who is affected
Work IT. Aimed mostly at company systems — you are affected through the companies you use, not your own phone.
What's at risk: Mass data theft and ransomware: a single flaw in a file-transfer or email server has exposed thousands of organisations at once.
The details
- Official name
- PHPMailer Command Injection Vulnerability
- Product
- PHP PHPMailer
- CISA description
- 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.
- Type of flaw
- Command or code injection (CWE-77, CWE-88)
- Confirmed exploited
- Jul 7, 2025
- US federal patch deadline
- Jul 28, 2025
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Answering about CVE-2016-10033 ·
Questions about CVE-2016-10033
Is CVE-2016-10033 being exploited?
Yes. CISA added CVE-2016-10033 to its Known Exploited Vulnerabilities catalog on Jul 7, 2025, which means there is reliable evidence of real-world attacks.
How do I fix CVE-2016-10033?
Install PHP's security update for PHPMailer. If no update exists, follow the vendor's workaround or stop using the product until one ships. Keep a list of every internet-facing server you run so nothing is forgotten.
Am I affected by CVE-2016-10033?
Only if you use PHP PHPMailer. Aimed mostly at company systems — you are affected through the companies you use, not your own phone.