CVE-2019-16701 in pfSense
Summary
by MITRE
pfSense through 2.3.4 through 2.4.4-p3 allows Remote Code Injection via a methodCall XML document with a pfsense.exec_php call containing shell metacharacters in a parameter value.
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Analysis
by VulDB Data Team • 09/08/2025
The vulnerability identified as CVE-2019-16701 represents a critical remote code execution flaw within pfSense firewall appliances running versions 2.3.4 through 2.4.4-p3. This vulnerability exists within the XMLRPC interface implementation that handles method calls, specifically targeting the pfsense.exec_php function which was designed to execute PHP code on the system. The flaw stems from insufficient input validation and sanitization of parameters passed to this function, creating an avenue for malicious actors to inject arbitrary shell commands that get executed with the privileges of the web server process.
The technical exploitation of this vulnerability occurs through crafting a malicious XML document containing a methodCall element with a pfsense.exec_php call. When the pfSense system processes this XML document, it fails to properly sanitize the parameters passed to the exec_php function, allowing shell metacharacters to be interpreted and executed by the underlying operating system. This represents a classic command injection vulnerability where user-controlled input flows directly into system execution contexts without proper sanitization. The Common Weakness Enumeration classification for this vulnerability aligns with CWE-77, which describes improper neutralization of special elements used in a command inside a web application, making it particularly dangerous in network security contexts where administrative access is often required.
The operational impact of this vulnerability extends beyond simple remote code execution to encompass full system compromise capabilities. An attacker with network access to the pfSense appliance can execute arbitrary commands with the privileges of the web server process, potentially leading to complete system takeover, data exfiltration, or use of the compromised device as a pivot point for attacking internal network resources. The vulnerability affects the XMLRPC interface which is commonly used for remote management and configuration of pfSense systems, making it particularly attractive to attackers targeting network security infrastructure. According to ATT&CK framework categorization, this vulnerability maps to T1059.001 (Command and Scripting Interpreter: PowerShell) and T1068 (Exploitation for Privilege Escalation) techniques, as it enables attackers to execute system commands and potentially escalate privileges within the network environment.
Mitigation strategies for CVE-2019-16701 focus on immediate patching of affected pfSense versions to the latest releases that contain proper input validation and sanitization for XMLRPC method calls. Organizations should also implement network segmentation to limit access to pfSense management interfaces, restrict XMLRPC access to trusted IP addresses only, and monitor network traffic for suspicious XMLRPC requests. Additionally, implementing web application firewalls and intrusion detection systems can help detect and block exploitation attempts. The vulnerability highlights the importance of proper input validation in web applications and the critical need for sanitizing user-supplied data before processing, particularly when executing system commands or handling administrative functions. Regular security audits and vulnerability assessments should be conducted to identify similar weaknesses in network infrastructure components, as this type of vulnerability can have cascading effects on network security posture and compliance requirements.