What it is
CVE-2016-10033 is an unauthenticated vulnerability affecting PHPMailer PHPMailer. The mailSend function in the isMail transport in PHPMailer before 5.2.18 might allow remote attackers to pass extra parameters to the...
Vulnerability report
Exploited in the wild
Confirmed confidence
In CISA KEV
CVE-2016-10033
PHPMailer
PHPMailer / PHPMailer
- Severity
- CVSS 9.8 · Critical
- Confidence
- Confirmed
- Exploit status
- Exploited in the wild
- EPSS
- 99.7%
- First observed
- —
- Last observed
- —
Decision summary
What security teams need to know first
Direct answers before the deeper technical record.
Is it exploited?
Yes. KEV Intelligence tracks this CVE as a known exploited vulnerability. Confidence is confirmed.
Who is affected?
PHPMailer / PHPMailer.
What should we do?
Prioritize remediation. Validate affected assets and apply vendor fixes on an accelerated timeline.
Overview
PHPMailer
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.
- Published
- 30 Dec 2016
- Exploitation Reported
- 01 Jun 2026
- Attack vector
- Remote
- Complexity
- Low
- Privileges
- None
- User interaction
- None
Tags
nuclei_scanner
cisa
php
CVE References
- CVE Record CVE.org · CVE Record https://www.cve.org/CVERecord?id=CVE-2016-10033
- 42221 exploit-db.com · Exploit https://www.exploit-db.com/exploits/42221/
- 40969 exploit-db.com · Exploit https://www.exploit-db.com/exploits/40969/
- 41962 exploit-db.com · Exploit https://www.exploit-db.com/exploits/41962/
- 40968 exploit-db.com · Exploit https://www.exploit-db.com/exploits/40968/
- 40974 exploit-db.com · Exploit https://www.exploit-db.com/exploits/40974/
- 40986 exploit-db.com · Exploit https://www.exploit-db.com/exploits/40986/
- 40970 exploit-db.com · Exploit https://www.exploit-db.com/exploits/40970/
- 41996 exploit-db.com · Exploit https://www.exploit-db.com/exploits/41996/
- 42024 exploit-db.com · Exploit https://www.exploit-db.com/exploits/42024/
- 95108 securityfocus.com · VDB Entry http://www.securityfocus.com/bid/95108
- 1037533 securitytracker.com · VDB Entry http://www.securitytracker.com/id/1037533
- 20161227 PHPMailer < 5.2.18 Remote Code Execution [updated advisory] [CVE-2016-10033] securityfocus.com · Mailing List http://www.securityfocus.com/archive/1/539963/100/0/threaded
- 20161227 PHPMailer < 5.2.18 Remote Code Execution [CVE-2016-10033] seclists.org · Mailing List http://seclists.org/fulldisclosure/2016/Dec/78
- packetstormsecurity.com/files/140350/PHPMailer-Sendmail-Argument-Inj... packetstormsecurity.com · CVE Record http://packetstormsecurity.com/files/140350/PHPMailer-Sendmail-Argume...
- drupal.org/psa-2016-004 drupal.org · CVE Record https://www.drupal.org/psa-2016-004
- legalhackers.com/advisories/PHPMailer-Exploit-Remote-Code-Exe... legalhackers.com · CVE Record https://legalhackers.com/advisories/PHPMailer-Exploit-Remote-Code-Exe...
- GitHub — PHPMailer/PHPMailer github.com · CVE Record https://github.com/PHPMailer/PHPMailer/releases/tag/v5.2.18
- GitHub — PHPMailer/PHPMailer github.com · CVE Record https://github.com/PHPMailer/PHPMailer/wiki/About-the-CVE-2016-10033-...
- packetstormsecurity.com/files/140291/PHPMailer-Remote-Code-Execution... packetstormsecurity.com · CVE Record http://packetstormsecurity.com/files/140291/PHPMailer-Remote-Code-Exe...
- rapid7.com/db/modules/exploit/multi/http/phpmailer_arg_... rapid7.com · CVE Record http://www.rapid7.com/db/modules/exploit/multi/http/phpmailer_arg_inj...
- developer.joomla.org/security-centre/668-20161205-phpmailer-secur... developer.joomla.org · CVE Record https://developer.joomla.org/security-centre/668-20161205-phpmailer-s...
Exploitation evidence
Why KEV Intelligence marks this CVE as exploited
Third-party attestation and first-party sensor observation are shown separately so teams can judge the evidence chain.
Exploited in the wild
CISA
Independent exploitation attestation added to the KEV Intelligence record.
Proof of concept available
GitHub
Public scanner or PoC coverage increases practical exploitability.
Known exploited vulnerability sources
Per-source evidence links for KEV attestations are available through the KEV Intelligence Pro API.
Learn about Pro API access| Source | Added |
|---|---|
| CVE First | 2026-06-01 10:36 UTC |
| CISA | 2026-06-02 14:07 UTC |
Detection
Operational artifacts and observed signals
Make the evidence actionable in scanner, SOC, and edge-control workflows.
Observed signals
- Request targets
- 0
- User-Agents
- 0
Raw values available in Pro and Enterprise.
Scanner coverage
Metasploit template detected 29 Apr 2025.
View Metasploit template (opens in new tab)Virtual patch status
No KEV Intelligence virtual patch is currently available. Future rules ship for ModSecurity, Cloudflare, and AWS WAF.
Learn about virtual patches →Scanner Artifacts
Scanner and exploit-framework references linked to this CVE.
| Scanner | Reference | Detected |
|---|---|---|
| Metasploit | https://github.com/rapid7/metasploit-framework/blob/master/modules/exploits/unix/webapp/wp_phpmailer_host_header.rb | 29 Apr 2025 |
| Nuclei | https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2016/CVE-2016-10033.yaml | 25 Apr 2025 |
Risk and context
Severity, weaknesses, and research context
CVSS v3.1
9.8
Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS
99.7%
All CVSS Scores
CVSS v3.1
9.8
Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CVSS v2.0
7.5
High
AV:N/AC:L/Au:N/C:P/I:P/A:P
Potential Proof of Concepts
These PoCs are unverified and could contain malware. Use at your own risk.
WordPress PHPMailer < 5.2.18 - Remote Code Execution
nuclei · Created Unknown
Timeline
From disclosure to observed exploitation
-
Added to CISA KEV
Listed in the CISA Known Exploited Vulnerabilities catalog
-
Added to KEV Intelligence KEV Feed
High-confidence, third-party attested exploitation
-
Metasploit module available
Exploit module available
-
Public PoC available
Public proof-of-concept code published
-
Nuclei template available
Scanner coverage available
-
CVE published
Vulnerability disclosed publicly
-
CVE ID reserved
Identifier reserved by the CNA
Pro API
Automate this intelligence
Confidence, exploit status, sensor telemetry, PoCs, scanner integrations, mentions, and tags are available programmatically for VM, SOC, and CTI workflows.
- Evidence confidence and provenance
- First-party sensor telemetry
- PoC and scanner references
- Affected versions and enrichment
- Automation-ready JSON delivery
GET /api/v2/pro/kevs/CVE-2016-10033
Free JSON includes basic KEV fields{
"cve_id": "CVE-2016-10033",
"confidence": "Confirmed",
"cvss_score": 9.8,
"cvss_estimated": false,
"epss_score": 0.99714,
"exploit_status": {
"exploited_in_the_wild": true,
"active_exploitation_observed": false
},
"sensor_telemetry": { "attempts": 0, "sensors": 0 }
}Early warning alerts
Get alerts on high-impact exploitation
Receive curator-selected alerts when exploitation activity warrants attention. Each alert includes the evidence and context needed to decide what requires attention now.