CVE-2018-6940 in NAT32
Summary
by MITRE
A /shell?cmd= XSS issue exists in the HTTPD component of NAT32 v2.2 Build 22284 devices that can be exploited for Remote Code Execution in conjunction with CSRF.
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Analysis
by VulDB Data Team • 11/16/2025
The vulnerability identified as CVE-2018-6940 represents a critical security flaw in the NAT32 v2.2 Build 22284 device firmware where a cross-site scripting vulnerability exists within the HTTPD component. This issue manifests through a /shell?cmd= parameter that allows malicious actors to inject arbitrary commands into the system. The vulnerability is particularly concerning because it operates within the web interface of network devices, providing attackers with a direct pathway to compromise the underlying system. The presence of the shell command parameter indicates that the device's web server is directly executing user-supplied commands without proper sanitization or validation, creating an inherent risk for unauthorized access and system manipulation.
The technical exploitation of this vulnerability follows a specific attack pattern that combines both cross-site scripting and cross-site request forgery elements to achieve remote code execution. When an attacker crafts a malicious payload containing shell commands within the cmd parameter, the vulnerable HTTPD component processes these commands directly without proper input filtering or sanitization mechanisms. This lack of input validation creates a pathway for attackers to execute arbitrary code on the target device, effectively bypassing normal security controls and gaining unauthorized access to system resources. The vulnerability's classification as CWE-79 - Cross-Site Scripting - indicates that the system fails to properly validate or escape user-supplied input before rendering it in web responses, while the combination with CSRF suggests that attackers can leverage legitimate user sessions to execute commands without requiring authentication.
The operational impact of this vulnerability extends beyond simple code execution to encompass complete system compromise of affected NAT32 devices. Once exploited, attackers can gain full control over the device's functionality, potentially allowing them to modify network configurations, redirect traffic, or establish persistent backdoors for continued access. The remote execution capability means that attackers do not need physical access to the device, making this vulnerability particularly dangerous in network environments where such devices are exposed to untrusted networks. The vulnerability affects the core network infrastructure components, potentially disrupting network operations and creating security gaps that could be exploited for broader attacks against connected systems. The combination of XSS and CSRF elements allows for sophisticated attack scenarios where attackers can manipulate device behavior without requiring direct user interaction beyond the initial exploitation.
Mitigation strategies for this vulnerability require immediate firmware updates from the vendor to address the input validation flaws in the HTTPD component. Network administrators should implement network segmentation and access controls to limit exposure of these devices to untrusted networks while monitoring for suspicious activities that might indicate exploitation attempts. The implementation of web application firewalls and input validation rules can provide additional protection layers to detect and block malicious payloads targeting this specific vulnerability. Security teams should also conduct comprehensive vulnerability assessments to identify all instances of affected NAT32 devices within their network infrastructure and ensure that proper network monitoring is in place to detect potential exploitation attempts. According to ATT&CK framework, this vulnerability maps to T1059 - Command and Scripting Interpreter and T1190 - Exploit Public-Facing Application, highlighting the attack vectors that should be monitored and protected against in enterprise security architectures. Organizations should also consider implementing network access control policies that restrict direct access to administrative interfaces and ensure that all network devices are regularly updated with the latest security patches to prevent similar vulnerabilities from being exploited.