Exploited vulnerability · CISA KEV

Is CVE-2016-10033 exploited? Yes: in CISA KEV since 7 Jul 2025

Gociux · PHPMailer · data: CISA KEV, CVE record, FIRST EPSS

Yes. CVE-2016-10033, PHPMailer Command Injection Vulnerability, is being exploited in the wild. CISA added it to its Known Exploited Vulnerabilities catalog on 7 Jul 2025, 3111 days after it was published. It affects PHPMailer. If you run it, CISA's required action is: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

What it is

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

1. Check whether you run it. Look for PHPMailer in your asset inventory, including appliances and cloud images. Stack check lists every exploited PHP CVE at once.
2. Apply the fix. Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
3. If you can't patch today, take the affected service off the internet or restrict who can reach it, and check its logs for signs of compromise since 30 Dec 2016.
4. Get told next time. Email alerts when CISA adds a CVE for PHP.

References

• github.com/advisories/GHSA-5f37-gxvh-23v6
• nvd.nist.gov/vuln/detail/CVE-2016-10033

Sources: CISA KEV (exploitation, ransomware use, required action, due date), the CVE record (publication date, CVSS, CNA), NVD and FIRST EPSS (live score). More: all KEV additions in July 2025 · PHP scorecard · act-now radar.