CVE-2021-38522 in R6400
Summary
by MITRE • 08/11/2021
NETGEAR R6400 devices before 1.0.1.52 are affected by a stack-based buffer overflow by an authenticated user.
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Analysis
by VulDB Data Team • 08/16/2021
The vulnerability identified as CVE-2021-38522 affects NETGEAR R6400 wireless routers running firmware versions prior to 1.0.1.52. This represents a critical security flaw that enables authenticated attackers to exploit a stack-based buffer overflow condition within the device's firmware. The vulnerability resides in the router's web interface handling of user input, specifically when processing certain parameters in HTTP requests. Attackers who have gained authentication credentials can leverage this flaw to execute arbitrary code on the affected device, potentially leading to complete system compromise. The stack-based buffer overflow occurs when the device fails to properly validate input length before copying data to a fixed-size buffer on the stack, creating a condition where malicious input can overwrite adjacent memory locations.
The technical exploitation of this vulnerability follows established patterns documented in CWE-121, which describes stack-based buffer overflow conditions where insufficient bounds checking allows attackers to overwrite stack memory. The attack vector requires an authenticated user, meaning that an attacker must first obtain valid login credentials through social engineering, credential reuse, or other means. Once authenticated, the attacker can submit malicious input through the router's web administration interface, specifically targeting parameters that are processed without adequate input validation. The overflow can potentially overwrite return addresses, function pointers, or other critical stack data, allowing for arbitrary code execution with the privileges of the web server process. This vulnerability directly maps to ATT&CK technique T1059.007 for command and script injection, as the successful exploitation enables attackers to execute commands on the compromised device.
The operational impact of CVE-2021-38522 extends beyond simple code execution, as it provides attackers with complete control over the affected router. This compromised device can then serve as a pivot point for further attacks within the local network, enabling man-in-the-middle attacks, DNS hijacking, or traffic interception. The router's role as a network gateway makes it particularly valuable to attackers, as it provides access to all devices connected to the local network. Additionally, the compromised device can be used to launch attacks against external targets, creating a botnet node or facilitating credential stuffing attacks against other services. The vulnerability's authenticated nature means that organizations with proper network segmentation and strong access controls may be partially protected, though this protection is not absolute given that credentials can be compromised through various attack vectors.
Mitigation strategies for CVE-2021-38522 should prioritize immediate firmware updates to version 1.0.1.52 or later, which contains the necessary patches to address the buffer overflow condition. Network administrators should also implement robust authentication controls including multi-factor authentication, strong password policies, and regular credential rotation. Monitoring network traffic for unusual patterns that might indicate exploitation attempts, such as unexpected HTTP requests or connections to suspicious external addresses, remains critical. Additionally, organizations should consider implementing network segmentation to limit the potential impact of a successful compromise, ensuring that even if one device is compromised, lateral movement within the network is restricted. Regular security assessments and vulnerability scanning should be conducted to identify other potentially vulnerable devices within the network infrastructure, as the presence of multiple vulnerable devices increases overall risk exposure. The remediation process should also include reviewing access logs for signs of unauthorized access and implementing proper network access controls to minimize the attack surface available to potential attackers.