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CVE-2016-10033

Remote code execution in PHPMailer

9.8 CriticalIn KEVPublic exploitFix available

CVE-2016-10033 is a critical vulnerability (CVSS 9.8) in Php Phpmailer, published December 30, 2016. CISA lists it as known to be exploited, since July 7, 2025. EUVD reports exploitation since July 7, 2025. Public exploit code exists. EPSS puts the chance of exploitation in the next 30 days at 99.7%, the 99th percentile. Fixed in phpmailer/phpmailer 5.2.18.

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.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
High
Integrity
High
Availability
High

Exploit likelihood

99.7%Up 3.4 points since Feb 4, 2022
90%50%10%1%

What each source reports

NVD Score used 9.8

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.

Record
CVE-2016-10033
CVSS 3.1
9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CVSS 2.0
7.5 HighAV:N/AC:L/Au:N/C:P/I:P/A:P
Weakness
CWE-88
Updated
2026-11-02
CVE List 9.8

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.

Record
CVE-2016-10033
CVSS 3.1
9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Weakness
CWE-88
Updated
2026-11-02
EUVDEUVD-2020-0331 9.8

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.

Record
EUVD-2020-0331
CVSS 3.1
9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Updated
2026-11-02
GitHub AdvisoriesGHSA-5f37-gxvh-23v6 9.8

Remote code execution in PHPMailer

Impact

The mailSend function in the default 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.

Patches

Fixed in 5.2.18

Workarounds

Filter and validate user input before passing it to internal functions.

References

https://nvd.nist.gov/vuln/detail/CVE-2016-10033 Related to a follow-on issue in https://nvd.nist.gov/vuln/detail/CVE-2016-10045

For more information

If you have any questions or comments about this advisory:

Record
GHSA-5f37-gxvh-23v6
CVSS 3.1
9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:H
Weakness
CWE-77, CWE-88
Updated
2026-11-02
CISA KEV No score

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.

Record
CVE-2016-10033
Weakness
CWE-77, CWE-88
Updated
2026-11-02
OSVALPINE-CVE-2016-10033 9.8

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.

Record
ALPINE-CVE-2016-10033
CVSS 3.1
9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Updated
2026-11-02
Show 6 moreShow less
OSV 9.8

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.

Record
CVE-2016-10033
CVSS 3.1
9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Updated
2026-11-02
OSVDEBIAN-CVE-2016-10033 9.8

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.

Record
DEBIAN-CVE-2016-10033
CVSS 3.1
9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Updated
2026-11-02
OSVGHSA-5f37-gxvh-23v6 9.8

Remote code execution in PHPMailer

Impact

The mailSend function in the default 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.

Patches

Fixed in 5.2.18

Workarounds

Filter and validate user input before passing it to internal functions.

References

https://nvd.nist.gov/vuln/detail/CVE-2016-10033 Related to a follow-on issue in https://nvd.nist.gov/vuln/detail/CVE-2016-10045

For more information

If you have any questions or comments about this advisory:

Record
GHSA-5f37-gxvh-23v6
CVSS 3.1
9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:H
Weakness
CWE-77, CWE-88
Updated
2026-11-02
OSVUBUNTU-CVE-2016-10033 9.8

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.

Record
UBUNTU-CVE-2016-10033
CVSS 3.1
9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CVSS 3.0
9.8 CriticalCVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Updated
2026-11-02
OSVMGASA-2017-0022 No score

Updated php-phpmailer packages fix security vulnerabilities

It was discovered that PHPMailer, a popular library to send email from PHP applications, allowed a remote attacker to execute code if they were able to provide a crafted Sender address (CVE-2016-10033).

It was discovered that PHPMailer prior to 5.2.22 contained a local file disclosure vulnerability if content passed to msgHTML() was sourced from unfiltered user input (CVE-2017-5223).

Record
MGASA-2017-0022
Updated
2026-11-02
OSVUSN-5956-1 No score

libphp-phpmailer vulnerabilities

Dawid Golunski discovered that PHPMailer was not properly escaping user input data used as arguments to functions executed by the system shell. An attacker could possibly use this issue to execute arbitrary code. This issue only affected Ubuntu 16.04 ESM. (CVE-2016-10033, CVE-2016-10045)

It was discovered that PHPMailer was not properly escaping characters in certain fields of the code_generator.php example code. An attacker could possibly use this issue to conduct cross-site scripting (XSS) attacks. This issue was only fixed in Ubuntu 16.04 ESM and Ubuntu 18.04 ESM. (CVE-2017-11503)

Yongxiang Li discovered that PHPMailer was not properly converting relative paths provided as user input when adding attachments to messages, which could lead to relative image URLs being treated as absolute local file paths and added as attachments. An attacker could possibly use this issue to access unauthorized resources and expose sensitive information. This issue only affected Ubuntu 16.04 ESM. (CVE-2017-5223)

Sehun Oh discovered that PHPMailer was not properly processing untrusted non-local file attachments, which could lead to an object injection. An attacker could possibly use this issue to execute arbitrary code. This issue only affected Ubuntu 16.04 ESM. (CVE-2018-19296)

Elar Lang discovered that PHPMailer was not properly escaping file attachment names, which could lead to a misinterpretation of file types by entities processing the message. An attacker could possibly use this issue to bypass attachment filters. This issue was only fixed in Ubuntu 16.04 ESM and Ubuntu 20.04 ESM. (CVE-2020-13625)

It was discovered that PHPMailer was not properly handling callables in its validateAddress function, which could result in untrusted code being called should the global namespace contain a function called 'php'. An attacker could possibly use this issue to execute arbitrary code. This issue was only fixed in Ubuntu 20.04 ESM and Ubuntu 22.04 ESM. (CVE-2021-3603)

Record
USN-5956-1
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
phpmailer/phpmailer
Packagist
5.0.0 up to 5.2.18
5.2.18
php-phpmailer
Alpine:v3.2
before 5.2.4-r0
5.2.4-r0
php-phpmailer
Alpine:v3.3
before 5.2.4-r0
5.2.4-r0
php5-phpmailer
Alpine:v3.4
before 5.2.0-r1
5.2.0-r1
php5-phpmailer
Alpine:v3.5
before 5.2.4-r1
5.2.4-r1
libphp-phpmailer
Debian:12
before 5.2.14+dfsg-2.1
5.2.14+dfsg-2.1
libphp-phpmailer
Debian:13
before 5.2.14+dfsg-2.1
5.2.14+dfsg-2.1
libphp-phpmailer
Debian:14
before 5.2.14+dfsg-2.1
5.2.14+dfsg-2.1
libphp-phpmailer
Debian:7
before 5.1-1.2, plus listed versions
5.1-15.1-1.1
5.1-1.2
libphp-phpmailer
Debian:8
before 5.2.9+dfsg-2+deb8u2, plus listed versions
5.2.9+dfsg-25.2.9+dfsg-2+deb8u1
5.2.9+dfsg-2+deb8u2
Show 6 moreShow less
Affected packages
PackageAffectedFixed
phpmailer/phpmailer
Packagist
5.0.0 up to 5.2.18, plus listed versions
v5.2.10v5.2.11v5.2.12v5.2.13v5.2.14
Show 10 moreShow less
v5.2.15v5.2.16v5.2.17v5.2.2v5.2.4v5.2.5v5.2.6v5.2.7v5.2.8v5.2.9
5.2.18
php-phpmailer
Mageia:5
before 5.2.22-1.mga5
5.2.22-1.mga5
libphp-phpmailer
Ubuntu:Pro:16.04:LTS
before 5.2.14+dfsg-1ubuntu0.1~esm1, plus listed versions
5.2.10+dfsg-15.2.14+dfsg-15.2.14+dfsg-1build1
5.2.14+dfsg-1ubuntu0.1~esm1
libphp-phpmailer
Ubuntu:Pro:18.04:LTS
before 5.2.14+dfsg-2.3+deb9u2ubuntu0.1~esm1, plus listed versions
5.2.14+dfsg-2.35.2.14+dfsg-2.3+deb9u1build0.18.04.15.2.14+dfsg-2.3+deb9u2build0.18.04.1
5.2.14+dfsg-2.3+deb9u2ubuntu0.1~esm1
libphp-phpmailer
Ubuntu:Pro:20.04:LTS
before 6.0.6-0.1ubuntu0.1~esm1, plus listed versions
6.0.6-0.1
6.0.6-0.1ubuntu0.1~esm1
libphp-phpmailer
Ubuntu:Pro:22.04:LTS
before 6.2.0-2ubuntu0.1~esm1, plus listed versions
6.2.0-2
6.2.0-2ubuntu0.1~esm1

Public exploits

Links only. Every CVE stores no exploit code.

Show 19 moreShow less
Public exploits
SourceLinkDate
PoC in GitHubGeneralTesler/CVE-2016-100332017-05-10
PoC in GitHubchipironcin/CVE-2016-100332017-05-10
Exploit-DBVanilla Forums < 2.3 - Remote Code Execution2017-05-11
Exploit-DBWordPress Plugin PHPMailer 4.6 - Host Header Command Injection (Metasploit)2017-05-17
PoC in GitHubBajunan/CVE-2016-100332017-05-19
Exploit-DBPHPMailer < 5.2.20 with Exim MTA - Remote Code Execution2017-06-21
PoC in GitHubliusec/WP-CVE-2016-100332017-07-22
PoC in GitHubpedro823/cve-2016-10033-452017-11-19
PoC in GitHubawidardi/opsxcq-cve-2016-100332018-02-06
PoC in GitHub0x00-0x00/CVE-2016-100332018-02-09
PoC in GitHubcved-sources/cve-2016-100332019-01-17
PoC in GitHubj4k0m/CVE-2016-100332021-08-31
PoC in GitHubzeeshanbhattined/exploit-CVE-2016-100332022-08-05
PoC in GitHubElnurBDa/CVE-2016-100332024-05-16
PoC in GitHubAstrowmist/POC-CVE-2016-100332024-05-22
PoC in GitHubsealldeveloper/CVE-2016-10033-PoC2025-04-25
PoC in GitHubalexander47777/CVE-2016-100332025-08-11
PoC in GitHubblue-chocolates/CVE-2016-100332026-07-24
NucleiWordPress PHPMailer < 5.2.18 - Remote Code Execution

History

History
WhenChangedSources
2026-11-03exploitation
2026-11-03exploits
2026-11-03exploits
2026-11-02createdCVE List, EUVD, Exploit-DB, GitHub Advisories, CISA KEV, Metasploit, Nuclei, NVD, OSV, PoC in GitHub

References

Show 39 moreShow less
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