CVE-2016-10033 — The mailSend function in the isMail transport in PHPMailer before 5

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.

01What is this vulnerability?

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.

02Affected products

No structured affected-product list available — see references below for vendor advisories.

03Active exploitation status

Yes — actively exploited. Added to the CISA KEV catalog on —.

04Recommended remediation

• Patch to a fixed version listed in the vendor advisory (see references below).
• Mitigate with WAF rules, network egress filters, or feature flags where the patch is not yet available.
• Hunt historical logs for exploitation indicators — see Detection signatures below.

05Technical details

For the full vendor write-up, exploit chains, and reference implementations, see the references list in section 09.

06Detection signatures

Open the Sigma generator with a pre-filled prompt for this CVE to draft a starting detection in your stack of choice:

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07Related CVEs

No directly-cited follow-up CVEs in the KB record for this advisory. The references list in section 09 carries the vendor cross-references.

08Timeline

• Published: 2016-12-30 (9y 7m ago)
• Last modified: 2026-06-17

09References

No additional references available in the KB record.