PHPMailer Command Injection Vulnerability - Recently added to CISA KEV.
Description
PHPMailer Command Injection Vulnerability - Recently added to CISA KEV.
AI Analyst Comment
Remediation
FEDERAL DEADLINE: July 27, 2025 (21 days). Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable. FEDERAL DEADLINE: July 27, 2025 (21 days). Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
CISA KEV Details
Deadline: July 27, 2025
Required Action: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
---METADATA---
VENDOR: PHP
PRODUCT: PHPMailer
AFFECTED_VERSIONS: Versions before 5.2.18
CONFIDENCE: high
MISSING: none
SOURCES_JSON: [{"url":"http://packetstormsecurity.com/files/140350/PHPMailer-Sendmail-Argument-Injection.html","name":null,"tags":["x_refsource_MISC"]},{"url":"https://www.drupal.org/psa-2016-004","name":null,"tags":["x_refsource_CONFIRM"]},{"url":"https://www.exploit-db.com/exploits/42221/","name":"42221","tags":["exploit","x_refsource_EXPLOIT-DB"]},{"url":"https://www.exploit-db.com/exploits/40969/","name":"40969","tags":["exploit","x_refsource_EXPLOIT-DB"]},{"url":"https://www.exploit-db.com/exploits/41962/","name":"41962","tags":["exploit","x_refsource_EXPLOIT-DB"]},{"url":"https://www.exploit-db.com/exploits/40968/","name":"40968","tags":["exploit","x_refsource_EXPLOIT-DB"]},{"url":"https://legalhackers.com/advisories/PHPMailer-Exploit-Remote-Code-Exec-CVE-2016-10033-Vuln.html","name":null,"tags":["x_refsource_MISC"]},{"url":"https://github.com/PHPMailer/PHPMailer/releases/tag/v5.2.18","name":null,"tags":["x_refsource_CONFIRM"]}]
PROFILE: batch@eb21ac00f78b
MODEL: gemini-3.1-flash-lite
GENERATED: 2026-08-29T19:15:03.194Z
---END_METADATA---
Description Summary:
A command injection vulnerability in PHPMailer allows unauthenticated remote attackers to execute arbitrary code by passing malicious parameters to the mail command via a crafted Sender property.
Executive Summary:
This critical remote code execution vulnerability in PHPMailer is currently being actively exploited in the wild, necessitating immediate patching.
Vulnerability Details
CVE-ID: CVE-2016-10033
Affected Software: PHP PHPMailer
Affected Versions: Versions before 5.2.18
Vulnerability: The vulnerability exists within the mailSend function of the isMail transport. An unauthenticated attacker can supply a specially crafted Sender property containing backslash-escaped double quotes, which allows them to inject extra parameters into the system mail command and trigger arbitrary code execution.
Business Impact
Successful exploitation of this vulnerability grants an attacker the ability to execute arbitrary code on the underlying server with the privileges of the web application. This poses a severe risk of total system compromise, unauthorized data exfiltration, and long-term persistence within the environment. Given the high CVSS score of 9.5 and confirmed active exploitation, this flaw represents an immediate and critical threat to business continuity.
Remediation Plan
Immediate Action: Update the PHPMailer library to version 5.2.18 or later immediately. If an update is not immediately feasible, disable the affected functionality or transition to a non-vulnerable mail transport mechanism.
Proactive Monitoring: Review web server and application logs for suspicious input parameters containing backslash or double-quote sequences, especially within contact form or mail-related submission fields. Monitor for unauthorized outgoing network connections or the creation of unexpected files in web-accessible directories.
Compensating Controls: Implement a Web Application Firewall (WAF) with rules configured to inspect and block malicious payloads targeting mail transport parameters. Ensure that the web application process runs with the least privilege necessary to limit the blast radius of a successful exploit.
Exploitation Status
Public Exploit Available: Yes, multiple functional exploits, including a Metasploit module and various ExploitDB entries (e.g., EDB-ID 42221, 40969), are publicly available.
Analyst Notes: This vulnerability is confirmed to be actively exploited in the wild as of July 2025. The flaw is highly accessible, as it does not require authentication and can be triggered via standard web input fields like contact forms.
Analyst Recommendation
The presence of confirmed active exploitation and the availability of weaponized exploits make this a top-tier security priority. Organizations must verify their software bill of materials to identify any instances of PHPMailer versions prior to 5.2.18 and apply the vendor-provided patch without delay. Failure to remediate this vulnerability significantly increases the likelihood of a successful system compromise.