CVE-2016-10033
CVE-2016-10033 is a critical-severity vulnerability in Phpmailer Project Phpmailer with a CVSS 3.x base score of 9.8. It is listed in CISA's Known Exploited Vulnerabilities (KEV) catalog, confirming it has been exploited in the wild (added 2025-07-07). The underlying weakness is classified as CWE-88.
Key facts
- Severity: Critical (CVSS 3.x base score 9.8)
- CVSS v2: 7.5
- EPSS exploit prediction: 100% (100th percentile)
- Actively exploited: Yes — listed in CISA KEV (added 2025-07-07)
- EU (EUVD) id: EUVD-2020-0331
- EU exploitation: Flagged exploited in the ENISA EU Vulnerability Database (since 2025-07-07)
- Weakness: CWE-88
- Affected product: Phpmailer Project Phpmailer
- Published:
- Last modified:
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.
Frequently asked questions
- What is CVE-2016-10033?
- 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 severe is CVE-2016-10033?
- CVE-2016-10033 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
- Is CVE-2016-10033 being actively exploited?
- Yes. CVE-2016-10033 is on CISA's Known Exploited Vulnerabilities (KEV) catalog, added on 2025-07-07, which means active exploitation has been confirmed. It should be prioritised for remediation.
- What products are affected by CVE-2016-10033?
- CVE-2016-10033 primarily affects Phpmailer Project Phpmailer. In total, 3 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
- How do I fix CVE-2016-10033?
- Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Because this CVE is known to be actively exploited, treat remediation as urgent — CISA KEV typically sets a short remediation deadline.
- Does CVE-2016-10033 have an EU (EUVD) identifier?
- Yes. CVE-2016-10033 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2020-0331. It is also flagged as exploited in the EUVD (since 2025-07-07).
- When was CVE-2016-10033 published?
- CVE-2016-10033 was published on 2016-12-30 and last updated on 2026-06-17.
References
- http://packetstormsecurity.com/files/140291/PHPMailer-Remote-Code-Execution.html
- http://packetstormsecurity.com/files/140350/PHPMailer-Sendmail-Argument-Injection.html
- http://seclists.org/fulldisclosure/2016/Dec/78
- http://www.rapid7.com/db/modules/exploit/multi/http/phpmailer_arg_injection
- http://www.securityfocus.com/archive/1/539963/100/0/threaded
- http://www.securityfocus.com/bid/95108
- http://www.securitytracker.com/id/1037533
- https://developer.joomla.org/security-centre/668-20161205-phpmailer-security-advisory.html
- https://github.com/PHPMailer/PHPMailer/releases/tag/v5.2.18
- https://github.com/PHPMailer/PHPMailer/wiki/About-the-CVE-2016-10033-and-CVE-2016-10045-vulnerabilities
- https://legalhackers.com/advisories/PHPMailer-Exploit-Remote-Code-Exec-CVE-2016-10033-Vuln.html
- https://www.drupal.org/psa-2016-004
- https://www.exploit-db.com/exploits/40968/
- https://www.exploit-db.com/exploits/40969/
- https://www.exploit-db.com/exploits/40970/
- https://www.exploit-db.com/exploits/40974/
- https://www.exploit-db.com/exploits/40986/
- https://www.exploit-db.com/exploits/41962/
- https://www.exploit-db.com/exploits/41996/
- https://www.exploit-db.com/exploits/42024/
- https://www.exploit-db.com/exploits/42221/
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2016-10033
Affected products (3)
- cpe:2.3:a:phpmailer_project:phpmailer:*:*:*:*:*:*:*:*
- cpe:2.3:a:wordpress:wordpress:*:*:*:*:*:*:*:*
- cpe:2.3:a:joomla:joomla\!:*:*:*:*:*:*:*:*
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