CVE-2022-43390 in NR7101
Summary
by MITRE • 01/11/2023
A command injection vulnerability in the CGI program of Zyxel NR7101 firmware prior to V1.15(ACCC.3)C0, which could allow an authenticated attacker to execute some OS commands on a vulnerable device by sending a crafted HTTP request.
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Analysis
by VulDB Data Team • 02/01/2023
The command injection vulnerability identified as CVE-2022-43390 affects the Zyxel NR7101 wireless router firmware version prior to V1.15(ACCC.3)C0, representing a critical security flaw that enables authenticated attackers to execute arbitrary operating system commands on the affected device. This vulnerability resides within the Common Gateway Interface (CGI) program component of the firmware, which serves as an interface between web server software and external applications. The flaw stems from insufficient input validation and sanitization of user-supplied data within the CGI processing logic, allowing maliciously crafted HTTP requests to bypass security controls and directly influence command execution paths. The vulnerability is particularly concerning because it requires only authentication to exploit, meaning that an attacker who has gained access to legitimate user credentials can leverage this weakness to escalate their privileges and gain full control over the router's operating system functionality.
The technical implementation of this vulnerability follows a classic command injection pattern where user-controllable input parameters are directly incorporated into system command execution without proper sanitization or escaping mechanisms. When the affected CGI program processes HTTP requests containing specially crafted payloads, it fails to properly validate or sanitize input fields that are subsequently used in command construction. This allows attackers to inject malicious commands that get executed with the privileges of the web server process, which typically runs with elevated permissions on the device. The vulnerability is classified as CWE-77 according to the CWE database, which specifically addresses command injection flaws where untrusted data is passed to system commands without proper validation or escaping. The attack vector involves sending a malicious HTTP request to the router's web interface, which then gets processed by the vulnerable CGI program and results in arbitrary command execution on the underlying operating system.
The operational impact of this vulnerability extends far beyond simple unauthorized command execution, as it provides attackers with complete control over the affected network device. An authenticated attacker can leverage this vulnerability to modify router configurations, disable security features, redirect network traffic, establish persistent backdoors, or use the device as a pivot point for further attacks within the network. The compromised router could serve as a launching pad for lateral movement attacks against other devices on the local network, potentially leading to broader security breaches. Additionally, the vulnerability could be exploited to create denial-of-service conditions by executing commands that crash or destabilize the router's operating system, or to exfiltrate sensitive configuration data and network information. This represents a significant risk for enterprise and home network environments where routers serve as critical infrastructure components, as the compromise of a single device can potentially affect multiple connected systems and users.
Mitigation strategies for CVE-2022-43390 should prioritize immediate firmware updates to version V1.15(ACCC.3)C0 or later, which contain patches that address the input validation and sanitization issues within the CGI program. Network administrators should also implement strict access controls and authentication mechanisms, including multi-factor authentication, to reduce the likelihood of unauthorized access to router management interfaces. Additional protective measures include network segmentation to isolate critical devices, regular monitoring of router logs for suspicious activity, and implementing web application firewalls to detect and block malicious HTTP requests. The vulnerability aligns with ATT&CK technique T1059.001 for command and scripting interpreter, specifically focusing on the execution of commands through web interfaces. Organizations should also consider conducting vulnerability assessments to identify other potential command injection vulnerabilities within their network infrastructure and implement robust input validation controls across all web applications and interfaces to prevent similar issues from occurring in the future.