Which products and versions are affected by CVE-2016-10033?

Affected: Joomla\!; Phpmailer (Phpmailer Project); Wordpress, among others. The full list is in the CVE brief.

Is CVE-2016-10033 being exploited in the wild?

It is exploited in the wild, listed in CISA KEV, Industry KEV feed, CIRCL KEV, ENISA EUVD since Jan 26, 2022.

Is CVE-2016-10033 in the CISA KEV catalog?

Yes. It was added on Jul 7, 2025 with a federal remediation due date of Jul 28, 2025.

Is there a public exploit for CVE-2016-10033?

Public exploit code is available.

Is there a fix for CVE-2016-10033?

Fixed versions are available, including Joomla\! 3.6.5, libphp-phpmailer 5.1-1.2, libphp-phpmailer 5.2.14+dfsg-1ubuntu0.1~esm1.

How urgently should CVE-2016-10033 be patched?

Brandefense priority: patch immediately, because it is listed as exploited in the wild.

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Vulnerability Intelligence

CVE-2016-10033

CriticalExploitedPublic exploit

Remote code execution in PHPMailer

Published Mar 5, 2020 · Updated Aug 4, 2026 · Also known as ALPINE-CVE-2016-10033, DEBIAN-CVE-2016-10033, DLA-770-1, DSA-3750-1, GHSA-5f37-gxvh-23v6, UBUNTU-CVE-2016-10033, USN-5956-1

Key Facts

Patch immediately

CVE-2016-10033 is a critical-severity vulnerability (CVSS 9.8 v3.1) affecting Joomla\!, Phpmailer (Phpmailer Project), Wordpress and 4 more products.
It is exploited in the wild, listed in CISA KEV, Industry KEV feed, CIRCL KEV, ENISA EUVD since Jan 26, 2022. Public exploit code is available.
EPSS estimates a 100% probability of exploitation in the next 30 days.
Fixed versions are available, including Joomla\! 3.6.5, libphp-phpmailer 5.1-1.2, libphp-phpmailer 5.2.14+dfsg-1ubuntu0.1~esm1.
Brandefense priority: patch immediately, because it is listed as exploited in the wild.

CVSS v3.1

9.8

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS (30-day exploit likelihood)

100%

Higher than 99.9% of all scored CVEs

Exploited in the wild

Yes

4 catalog listings

Public exploit code

Available

Proof-of-concept or weaponized module

Get the full CVE-2016-10033 brief as a PDF

Every affected product and fixed release, exploitation status and a first 24 hours response checklist, emailed within minutes.

Description

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.

Known-Exploited Catalog Listings

Catalog	Added	Remediation due	Ransomware use
CISA KEV	Jul 7, 2025	Jul 28, 2025	Not reported
Industry KEV feed	Jan 26, 2022	Jul 28, 2025	Not reported
CIRCL KEV	Jul 7, 2025	Jul 28, 2025	Not reported
ENISA EUVD	Jul 7, 2025	n/a	Not reported

Required action: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

Affected Products

27 affected entries in total

Product	Affected versions	Fixed in
Joomla\!Joomla	See advisory	3.6.5
PhpmailerPhpmailer Project	See advisory	5.2.18
WordpressWordpress	See advisory	4.7
php5-phpmaileralpine	See advisory	5.2.0-r1
php-phpmaileralpine	See advisory	5.2.4-r0

2 more affected products in the full CVE brief

Patched Releases

Joomla\!

3.6.5

libphp-phpmailer

5.1-1.2, 5.2.14+dfsg-1ubuntu0.1~esm1, 5.2.14+dfsg-2.1, 5.2.14+dfsg-2.3+deb9u2ubuntu0.1~esm1, 5.2.9+dfsg-2+deb8u2, 6.0.6-0.1ubuntu0.1~esm1, 6.2.0-2ubuntu0.1~esm1

php-phpmailer

5.2.4-r0

php5-phpmailer

5.2.0-r1, 5.2.4-r1

Phpmailer

5.2.18

phpmailer/phpmailer

5.2.18

Wordpress

4.7.1-1, 4.7

Timeline

Publicly disclosed
Mar 5, 2020
Added to Industry KEV feed
Jan 26, 2022
Added to CISA KEV
Jul 7, 2025
Added to CIRCL KEV
Jul 7, 2025
Added to ENISA EUVD
Jul 7, 2025
Last updated
Aug 4, 2026

Weakness Type

CWE-77 Improper Neutralization of Special Elements used in a Command ('Command Injection')
CWE-88 Improper Neutralization of Argument Delimiters in a Command ('Argument Injection')

References

15 more references in the full CVE brief

FAQ

Common Questions.

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.
Affected: Joomla\!; Phpmailer (Phpmailer Project); Wordpress, among others. The full list is in the CVE brief.
It is exploited in the wild, listed in CISA KEV, Industry KEV feed, CIRCL KEV, ENISA EUVD since Jan 26, 2022.
Yes. It was added on Jul 7, 2025 with a federal remediation due date of Jul 28, 2025.
Public exploit code is available.
Fixed versions are available, including Joomla\! 3.6.5, libphp-phpmailer 5.1-1.2, libphp-phpmailer 5.2.14+dfsg-1ubuntu0.1~esm1.
Brandefense priority: patch immediately, because it is listed as exploited in the wild.

Is CVE-2016-10033 Running On Your Attack Surface?

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