The mailSend function in the isMail transport in PHPMailer before 5.2.18 might allow remote attackers to pass extra parameters to the mail c
PHPMailer versions before 5.2.18 are affected when they use the default PHP mail() transport (isMail). The fix is in PHPMailer 5.2.18.
- Published
- Last modified
- Where the record stands: published, rejected by its publisher, or superseded by another id.What do these mean? →
- published
- Whether CISA lists it in its Known Exploited Vulnerabilities catalog: proof that attackers are using it.What do these mean? →
- Listed in CISA KEV
- How many real-world setups can hit the bug, from the vendor's advisory and CISA data. It does not know your setup.What do these mean? →
- Actively exploited
- Fix
- Fixed in 5.2.18
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
Summary
PHPMailer, a popular PHP library for sending email, is affected through its isMail transport, where the mailSend function may let remote attackers inject extra parameters into the mail command. This could allow an attacker to execute arbitrary code on the server hosting the application.
Summarized by anthropic/claude-haiku-5.5. Verify details against the original sources.
Read the original 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.
Timeline
- CVE published
- Added to CISA KEV
CISA has evidence of exploitation in the wild
- CISA remediation deadline
Due date for US federal agencies to patch
- Record last updated
- EPSS reached 10%
FIRST estimates at least a 10% chance of exploitation in the next 30 days
Affected versions
- n/a n/a
Version range not reported
- phpmailer/phpmailerPackagist
From 5.0.0 · fixed in 5.2.18
References 21
packetstormsecurity.com
drupal.org
Exploit-DB
GitHub · PHPMailer/PHPMailer
securityfocus.com
seclists.org
securitytracker.com
developer.joomla.org
Questions about CVE-2016-10033
What does this mean?
The mailSend function in the isMail transport can let remote attackers pass extra parameters to the mail command. The vendor describes the impact as remote arbitrary code execution as the web server user, which could lead to full compromise of the web application.Source: drupal.org, legalhackers.com
Am I affected, and how do I check?
PHPMailer versions from 5.0.0 up to but not including 5.2.18 are affected, in setups where PHPMailer uses the PHP mail() function as its default transport. To check, look at the installed phpmailer/phpmailer version and whether the transport is still the default PHP mail() function.Source: drupal.org, legalhackers.com
What should I do about it?
Upgrade PHPMailer to version 5.2.18, which the vendor released as a critical security release to fix the issue.Source: drupal.org, legalhackers.com
Is it being exploited?
Yes. CISA added it to its Known Exploited Vulnerabilities catalog on 2025-07-07, which means it has evidence of attacks. No public exploit code is tracked.Source: cisa.gov, cve.now feed data