CVE-2018-4031 in Smart Firewall
Summary
by MITRE
An exploitable vulnerability exists in the safe browsing function of the CUJO Smart Firewall, version 7003. The flaw lies in the way the safe browsing function parses HTTP requests. The server hostname is extracted from captured HTTP/HTTPS requests and inserted as part of a Lua statement without prior sanitization, which results in arbitrary Lua script execution in the kernel. An attacker could send an HTTP request to exploit this vulnerability.
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Analysis
by VulDB Data Team • 02/01/2024
The CVE-2018-4031 vulnerability represents a critical security flaw in the CUJO Smart Firewall's safe browsing functionality, specifically targeting version 7003. This vulnerability demonstrates a classic server-side code injection weakness that allows remote attackers to execute arbitrary code within the device's kernel environment. The flaw stems from inadequate input validation and sanitization processes within the firewall's web filtering mechanisms, creating a pathway for malicious actors to compromise the device's core operations.
The technical implementation of this vulnerability occurs during HTTP request processing within the safe browsing function. When the firewall intercepts HTTP/HTTPS traffic, it extracts the server hostname from incoming requests to perform domain validation or filtering operations. However, the system fails to properly sanitize this extracted hostname before incorporating it into Lua script statements that execute within the kernel space. This omission creates a direct code injection vector where attacker-controlled data can be interpreted as executable Lua code rather than mere string data.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it provides attackers with complete control over the firewall's kernel operations. The arbitrary Lua script execution capability allows malicious actors to manipulate the device's core functionality, potentially enabling them to bypass security measures, redirect traffic, or even install persistent backdoors. This represents a severe compromise of the device's primary security function, as the firewall becomes vulnerable to attacks that undermine its protective capabilities rather than simply being a target for exploitation.
The vulnerability aligns with CWE-94, which describes "Improper Control of Generation of Code ('Code Injection')" and follows patterns consistent with the ATT&CK framework's technique T1059.007 for "Command and Scripting Interpreter: Lua." The flaw demonstrates how insufficient input validation in network security appliances can create dangerous attack vectors that undermine the fundamental security posture of the device. Organizations relying on CUJO firewalls for network protection face significant risk of unauthorized access and potential network compromise.
Mitigation strategies for CVE-2018-4031 require immediate firmware updates from the vendor to address the sanitization deficiency in the hostname parsing logic. Network administrators should implement network segmentation and monitoring to detect unusual traffic patterns that might indicate exploitation attempts. Additionally, the vulnerability highlights the importance of proper input validation and the principle of least privilege in embedded security systems, particularly those handling network traffic filtering. The incident underscores the critical need for security testing of all code execution paths within network appliances, especially those operating in kernel space where privilege escalation can lead to complete system compromise.