CVE-2021-20166 in RAX43
Summary
by MITRE • 12/31/2021
Netgear RAX43 version 1.0.3.96 contains a buffer overrun vulnerability. The URL parsing functionality in the cgi-bin endpoint of the router containers a buffer overrun issue that can redirection control flow of the applicaiton.
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Analysis
by VulDB Data Team • 01/05/2022
The vulnerability identified as CVE-2021-20166 affects Netgear RAX43 routers running firmware version 1.0.3.96 and represents a critical buffer overrun flaw within the device's web interface. This issue resides in the URL parsing functionality of the cgi-bin endpoint, which serves as a crucial interface for router administration and configuration. The buffer overrun vulnerability stems from inadequate input validation and memory management within the router's web server component, specifically when processing HTTP requests containing malformed or excessively long URLs. The flaw allows an attacker to manipulate the application's control flow through crafted URL parameters, potentially leading to arbitrary code execution or complete system compromise. This vulnerability is particularly concerning as it affects a widely deployed consumer-grade router model, making it accessible to a broad range of potential attackers. The issue manifests when the router processes URLs that exceed the allocated buffer space, causing memory corruption that can be exploited to overwrite critical program execution pointers or stack variables.
The technical exploitation of this vulnerability aligns with CWE-121, which describes heap-based buffer overflow conditions, and CWE-122, which covers stack-based buffer overflow scenarios. From an operational perspective, this vulnerability enables attackers to perform remote code execution without requiring authentication, as the flaw exists within the unauthenticated web interface. The attack surface is extensive since the cgi-bin endpoint is designed to handle various administrative functions and configuration requests, making it a prime target for exploitation. Attackers can leverage this vulnerability to redirect the router's execution flow, potentially gaining root access to the device and establishing persistent control over the network infrastructure. The impact extends beyond individual device compromise, as compromised routers can serve as launching points for broader network attacks, including man-in-the-middle operations, DNS poisoning, or as part of botnet formations.
The operational implications of CVE-2021-20166 are severe and multifaceted, particularly when considering the ATT&CK framework's T1059.007 technique for command and scripting interpreter execution. Once exploited, attackers can execute arbitrary commands on the affected router, potentially modifying firewall rules, redirecting traffic, or installing persistent backdoors. The vulnerability's location within the router's web server component means that exploitation can occur through standard web browser interactions, making it accessible to attackers with minimal technical expertise. Network reconnaissance activities can easily identify vulnerable devices, as the affected firmware versions are commonly deployed in residential and small office environments. The attack vector is particularly dangerous because it can be initiated through web-based attacks, potentially through malicious links or compromised websites that direct users to exploit the vulnerability. The lack of authentication requirements means that any internet-facing device with this vulnerability can be compromised without the need for credentials, significantly increasing the attack surface and potential impact. Organizations and individuals should prioritize immediate firmware updates to address this vulnerability, as the risk of exploitation remains high given the widespread deployment of affected Netgear devices.
Mitigation strategies should focus on immediate firmware updates from Netgear, as the vendor has released patches addressing this specific buffer overrun vulnerability. Network segmentation and firewall rules should be implemented to restrict access to the router's web interface from untrusted networks, particularly limiting access to the cgi-bin endpoint. Regular network monitoring should include detection of unusual traffic patterns or attempts to access the vulnerable endpoint. The implementation of network access control lists can prevent unauthorized access to administrative interfaces, while intrusion detection systems should be configured to alert on suspicious URL patterns that may indicate exploitation attempts. Device hardening practices, including disabling unnecessary services and ports, can reduce the attack surface. Organizations should consider implementing automated patch management systems to ensure timely deployment of security updates across all networked devices. Additionally, network administrators should conduct regular vulnerability assessments to identify other potentially affected devices and ensure that all firmware versions are current with the latest security patches. The vulnerability serves as a reminder of the importance of secure coding practices and proper input validation in embedded systems, particularly in network infrastructure devices that are frequently targeted by cybercriminals.