CVE-2016-10033

Phpmailer Project Phpmailer ≤ 5.2.18

CISA KEVActive ExploitationEUVD ExploitedPublic PoC

Published

30 December 2016

Modified

21 April 2026

KEV Added

07 July 2025

Patch / advisory

View advisory

CVSS Score v3.1 9.8

Click a component to see what it means

Raw vector

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

EPSS Score 0.99 100.0th percentile

Risk Priority 97 floored blend · peak EPSS

CVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.

Summary

CVE-2016-10033 is a critical-severity Argument Injection (CWE-88) vulnerability in Phpmailer Project Phpmailer. Its CVSS base score is 9.8 (Critical).

Operationally, exploitation aligns with the MITRE ATT&CK technique Junk Data (T1001.001); ranked in the top 0.0% of CVEs by exploit likelihood; CISA has added it to the Known Exploited Vulnerabilities catalog; a public proof-of-concept is referenced.

Deeper analysis AI-assisted summary

Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.

The vulnerability CVE-2016-10033 is present in the mailSend function of the isMail transport in PHPMailer versions before 5.2.18. It arises from insufficient neutralization of the Sender property, allowing a backslash double quote sequence to inject additional arguments into the mail command and is tracked as CWE-88 with a CVSS 3.1 score of 9.8.

Unauthenticated remote attackers can supply a crafted Sender value when an application uses the vulnerable PHPMailer instance to send mail. This permits arbitrary parameters to be passed to the mail binary, enabling execution of attacker-controlled commands on the underlying system.

Public exploit code and Metasploit modules demonstrating the injection are referenced in disclosures on PacketStorm, Seclists full-disclosure, and Rapid7, confirming that the issue is remotely exploitable in default configurations without requiring user interaction.

OWASP Top 10 for Web (2025)

EU & UK References

🇪🇺 ENISA EUVD: EUVD-2020-0331

Vulnerability Data

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.

CWE(s): CWE-88
KEV Date Added: 07 July 2025

Related Threats

MITRE ATT&CK Enterprise Techniques

T1001.001 Junk Data Command And Control

Adversaries may add junk data to protocols used for command and control to make detection more difficult.

attack.mitre.org →

T1003.002 Security Account Manager Credential Access

Adversaries may attempt to extract credential material from the Security Account Manager (SAM) database either through in-memory techniques or through the Windows Registry where the SAM database is stored.

attack.mitre.org →

T1003.003 NTDS Credential Access

Adversaries may attempt to access or create a copy of the Active Directory domain database in order to steal credential information, as well as obtain other information about domain members such as devices, users, and access rights.

attack.mitre.org →

T1003.004 LSA Secrets Credential Access

Adversaries with SYSTEM access to a host may attempt to access Local Security Authority (LSA) secrets, which can contain a variety of different credential materials, such as credentials for service accounts.

attack.mitre.org →

T1003.007 Proc Filesystem Credential Access

Adversaries may gather credentials from the proc filesystem or `/proc`.

attack.mitre.org →

T1011.001 Exfiltration Over Bluetooth Exfiltration

Adversaries may attempt to exfiltrate data over Bluetooth rather than the command and control channel.

attack.mitre.org →

Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2016-10045Same product: Joomla Joomla\!

CVE-2023-23752Same product: Joomla Joomla\!both on KEV

CVE-2026-87902Same product: Wordpress Wordpressboth on KEV

CVE-2026-60137Same product: Wordpress Wordpressboth on KEV

CVE-2026-63030Same product: Wordpress Wordpressboth on KEV

CVE-2026-86060Shared CWE-88both on KEV

CVE-2026-24061Shared CWE-88both on KEV

CVE-2024-41710Shared CWE-88both on KEV

CVE-2018-7602Same product class: CMS coreboth on KEV

CVE-2024-31210Same product: Wordpress Wordpress

Affected Assets

phpmailer project

phpmailer

≤ 5.2.18

wordpress

≤ 4.7

joomla

joomla\!

1.5.0 — 3.6.5

Mitigating Controls

Control response

Prevent

Stop it (NIST 800-53)

—

Detect

Catch it (NIST detect / respond)

—

Harden

Shrink the surface (DISA STIG)

—

Validate

Prove the fix (OWASP ASVS)

V1.2.5

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.PS-06 partial match

blocks

Secure SDLC practices directly require proper input validation and command construction to prevent argument injection.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.5.14 Information transfer partial match

removes

A.5.15 Access control partial match

removes

A.5.16 Identity management partial match

removes

A.5.17 Authentication information partial match

removes

A.5.18 Access rights partial match

removes

A.5.3 Segregation of duties partial match

removes

References

http://packetstormsecurity.com/files/140291/PHPMailer-Remote-Code-Execution.html
Exploit, Third Party Advisory, VDB Entry · cve@mitre.org
http://packetstormsecurity.com/files/140350/PHPMailer-Sendmail-Argument-Injection.html
Exploit, Third Party Advisory, VDB Entry · cve@mitre.org
http://seclists.org/fulldisclosure/2016/Dec/78
Mailing List, Patch, Third Party Advisory · cve@mitre.org
http://www.rapid7.com/db/modules/exploit/multi/http/phpmailer_arg_injection
Exploit, Third Party Advisory · cve@mitre.org
http://www.securityfocus.com/archive/1/539963/100/0/threaded
Broken Link, Third Party Advisory, VDB Entry · cve@mitre.org
http://www.securityfocus.com/bid/95108
Broken Link, Exploit, Third Party Advisory, VDB Entry · cve@mitre.org
http://www.securitytracker.com/id/1037533
Broken Link, Third Party Advisory, VDB Entry · cve@mitre.org
https://developer.joomla.org/security-centre/668-20161205-phpmailer-security-advisory.html
Third Party Advisory · cve@mitre.org
https://github.com/PHPMailer/PHPMailer/releases/tag/v5.2.18
Patch, Vendor Advisory · cve@mitre.org
https://github.com/PHPMailer/PHPMailer/wiki/About-the-CVE-2016-10033-and-CVE-2016-10045-vulnerabilities
Patch, Vendor Advisory · cve@mitre.org
https://legalhackers.com/advisories/PHPMailer-Exploit-Remote-Code-Exec-CVE-2016-10033-Vuln.html
Exploit, Patch, Third Party Advisory · cve@mitre.org
https://www.drupal.org/psa-2016-004
Third Party Advisory · cve@mitre.org
https://www.exploit-db.com/exploits/40968/
Exploit, Patch, Third Party Advisory, VDB Entry · cve@mitre.org
https://www.exploit-db.com/exploits/40969/
Exploit, Third Party Advisory, VDB Entry · cve@mitre.org
https://www.exploit-db.com/exploits/40970/
Exploit, Patch, Third Party Advisory, VDB Entry · cve@mitre.org
https://www.exploit-db.com/exploits/40974/
Exploit, Third Party Advisory, VDB Entry · cve@mitre.org
https://www.exploit-db.com/exploits/40986/
Exploit, Third Party Advisory, VDB Entry · cve@mitre.org
https://www.exploit-db.com/exploits/41962/
Exploit, Third Party Advisory, VDB Entry · cve@mitre.org
https://www.exploit-db.com/exploits/41996/
Exploit, Third Party Advisory, VDB Entry · cve@mitre.org
https://www.exploit-db.com/exploits/42024/
Exploit, Third Party Advisory, VDB Entry · cve@mitre.org