CVE-2016-10033
CRITICALCISA KEVEPSS 100th pctlDescription
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.
How to fix
TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works
Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.
CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Exploit Intelligence
Very high risk: more likely to be exploited than 100% of all known CVEs.
PHPMailer Command Injection Vulnerability
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.
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Remediation due: 2025-07-28
References
Related Vulnerabilities
Other CWE-88 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2022-36804 | High | 8.8 | 99% | KEV | Fix |
| CVE-2026-24061 | Critical | 9.8 | 98% | KEV | Fix |
| CVE-2007-0882 | High | 10.0 | 98% | - | - |
| CVE-2018-17456 | Critical | 9.8 | 97% | - | Fix |
| CVE-2018-19518 | High | 7.5 | 95% | - | Fix |
| CVE-2021-33564 | Critical | 9.8 | 72% | - | Fix |
Common questions
How do I fix CVE-2016-10033?
Published advisories record a fix for 2 affected products. The "How to fix" section on this page lists the fixed version and source advisory for each one, so apply the entry matching what you actually run.
Is CVE-2016-10033 being actively exploited?
Yes. CVE-2016-10033 is listed in the CISA Known Exploited Vulnerabilities catalog, which means exploitation has been observed in the wild. US federal agencies were required to remediate it by 2025-07-28. Treat it as a priority whatever its CVSS score says.
How severe is CVE-2016-10033?
CVE-2016-10033 has a CVSS v3 base score of 9.8, rated critical. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
What does CVE-2016-10033 affect?
Published advisories record a fix for libphp-phpmailer (Debian), libphp-phpmailer (Ubuntu). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-04-21.