CVE-2021-38530 in RBK40
Summary
by MITRE • 08/11/2021
Certain NETGEAR devices are affected by command injection by an unauthenticated attacker. This affects RBK40 before 2.5.1.16, RBR40 before 2.5.1.16, RBS40 before 2.5.1.16, RBK20 before 2.5.1.16, RBR20 before 2.5.1.16, RBS20 before 2.5.1.16, RBK50 before 2.5.1.16, RBR50 before 2.5.1.16, RBS50 before 2.5.1.16, and RBS50Y before 2.6.1.40.
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Analysis
by VulDB Data Team • 08/16/2021
This vulnerability represents a critical command injection flaw in NETGEAR wireless routers and access points that affects multiple device models including RBK40, RBR40, RBS40, RBK20, RBR20, RBS20, RBK50, RBR50, RBS50, and RBS50Y. The vulnerability stems from insufficient input validation in the web interface handling of specific parameters, allowing unauthenticated remote attackers to execute arbitrary commands on affected devices. This issue falls under the common weakness enumeration CWE-77 which specifically addresses command injection vulnerabilities where untrusted data is incorporated into system commands without proper sanitization or validation. The flaw exists in the authentication handling mechanism of these devices, creating a pathway for attackers to bypass normal access controls and gain unauthorized execution capabilities on the underlying operating system.
The technical exploitation of this vulnerability occurs through the manipulation of web interface parameters that are processed by the device's command execution engine. Attackers can craft malicious requests that include shell metacharacters and command sequences which are then interpreted and executed by the device's underlying operating system. This allows for complete compromise of the affected network infrastructure, enabling attackers to gain full administrative control over the devices and potentially use them as entry points for further network infiltration. The vulnerability specifically impacts devices running firmware versions prior to the mentioned patches, making the entire product line susceptible to exploitation without requiring any credentials or authentication.
From an operational perspective, this vulnerability creates significant risk for network security and infrastructure integrity. An attacker can leverage this flaw to execute commands such as creating backdoors, modifying network configurations, redirecting traffic, or even installing malware on the affected devices. The impact extends beyond individual device compromise to potentially affect entire network segments that rely on these devices for connectivity and access control. According to ATT&CK framework, this vulnerability maps to technique T1059.001 for command and scripting interpreter and T1068 for exploit for privilege escalation, as attackers can use the compromised devices to pivot and escalate their access within the network environment. The lack of authentication requirements makes this particularly dangerous as it allows for automated exploitation at scale.
Network security teams should immediately prioritize patching all affected devices with the vendor-provided firmware updates that address this vulnerability. The recommended mitigation strategy includes implementing network segmentation to limit the potential impact of compromised devices, monitoring network traffic for suspicious command execution patterns, and deploying intrusion detection systems that can identify exploitation attempts. Organizations should also consider implementing network access controls to restrict access to administrative interfaces and ensure that only authorized personnel can interact with these devices. The vulnerability demonstrates the critical importance of regular firmware updates and proper input validation in embedded systems, particularly in network infrastructure devices where a single flaw can compromise entire network environments. Additionally, security monitoring should focus on identifying unusual command execution patterns and unauthorized access attempts to these specific device models.