CVE-2018-4019 in pfSense
Summary
by MITRE
An exploitable command injection vulnerability exists in the way Netgate pfSense CE 2.4.4-RELEASE processes the parameters of a specific POST request. The attacker can exploit this and gain the ability to execute arbitrary commands on the system. An attacker needs to be able to send authenticated POST requests to the administration web interface. Command injection is possible in the `powerd_normal_mode` parameter.
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Analysis
by VulDB Data Team • 06/12/2023
The vulnerability described in CVE-2018-4019 represents a critical command injection flaw within the pfSense community edition version 2.4.4-RELEASE network security platform. This issue resides in the web administration interface processing logic where specific POST requests containing unvalidated parameters are handled. The vulnerability specifically affects the `powerd_normal_mode` parameter which is processed without proper input sanitization, creating a pathway for malicious command execution. As a community edition product widely deployed in enterprise and small business environments, pfSense serves as a critical firewall and router management platform, making this vulnerability particularly dangerous due to its potential for widespread impact across network infrastructures.
The technical exploitation of this vulnerability occurs through authenticated POST requests sent to the web administration interface, requiring an attacker to have valid credentials to access the system. The flaw manifests when the system processes the `powerd_normal_mode` parameter without implementing adequate validation or sanitization measures, allowing attackers to inject malicious commands that get executed within the context of the web server process. This type of vulnerability maps directly to CWE-77 which defines command injection as the improper handling of externally supplied input that is interpreted as commands by the operating system. The attack vector specifically targets the web interface's parameter processing mechanism, where user-supplied data flows directly into system command execution contexts without proper filtering or escaping.
The operational impact of this vulnerability extends beyond simple privilege escalation as it provides attackers with full system command execution capabilities on the affected pfSense appliance. This means that an authenticated attacker can execute arbitrary code with the privileges of the web server process, typically running as root or with administrative privileges on the system. The implications are severe for network security infrastructure, as pfSense appliances often serve as the primary gateway for network traffic control and firewall management. Attackers could potentially modify firewall rules, disable security features, exfiltrate network traffic, or establish persistent access points within the network infrastructure, effectively compromising the entire security posture of the organization relying on the platform.
Mitigation strategies for this vulnerability require immediate patching of the pfSense community edition to version 2.4.4-RELEASE-p1 or later, which contains the necessary fixes to address the command injection flaw. Network administrators should also implement additional security controls including restricting access to the web administration interface through network segmentation, implementing strong authentication mechanisms, and monitoring for suspicious POST request patterns. The mitigation approach aligns with ATT&CK technique T1059.001 which covers command and scripting interpreter execution, emphasizing the need for input validation and proper parameter handling in web applications. Organizations should also consider implementing web application firewalls and regular security assessments to detect and prevent similar vulnerabilities in other components of their network infrastructure.