CVE-2021-38538 in D7800
Summary
by MITRE • 08/11/2021
Certain NETGEAR devices are affected by stored XSS. This affects D7800 before 1.0.1.56, R7800 before 1.0.2.68, R8900 before 1.0.4.26, R9000 before 1.0.4.26, RAX120 before 1.0.0.78, RBK20 before 2.3.5.26, RBR20 before 2.3.5.26, RBS20 before 2.3.5.26, RBK40 before 2.3.5.30, RBR40 before 2.3.5.30, RBS40 before 2.3.5.30, RBK50 before 2.3.5.30, RBR50 before 2.3.5.30, RBS50 before 2.3.5.30, and XR500 before 2.3.2.56.
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Analysis
by VulDB Data Team • 08/16/2021
The vulnerability CVE-2021-38538 represents a stored cross-site scripting flaw affecting multiple NETGEAR router models, specifically targeting devices in the D7800, R7800, R8900, R9000, RAX120, and various RBK, RBR, and RBS series routers. This security weakness resides in the web-based management interface of these networking devices, creating a persistent threat vector that can be exploited by attackers who gain access to the device's administrative functions. The vulnerability allows malicious actors to inject malicious scripts that persistently execute within the context of the victim's browser when other users access the affected device's web interface.
The technical implementation of this stored XSS vulnerability stems from insufficient input validation and output encoding within the affected NETGEAR firmware implementations. When administrators or users interact with the web management interface, the system fails to properly sanitize user-supplied input before storing and subsequently rendering it within web pages. This flaw operates under CWE-79 which classifies cross-site scripting as a critical weakness in web applications, where the application fails to validate or escape user input before including it in dynamically generated web content. The vulnerability is particularly concerning because it affects a wide range of consumer and small business networking equipment, making it a prime target for widespread exploitation.
The operational impact of this vulnerability extends beyond simple script execution, as it provides attackers with the capability to establish persistent access to network infrastructure. An attacker who successfully exploits this vulnerability could potentially steal administrative credentials, modify router configurations, redirect traffic, or establish backdoor access points within the network. The stored nature of the vulnerability means that once exploited, the malicious payload remains active even after the initial attack window, allowing for sustained compromise of the affected network devices. This aligns with ATT&CK technique T1071.004 for application layer protocol: DNS and T1566.001 for credential harvesting through social engineering, as attackers can leverage the compromised devices for further network infiltration.
Mitigation strategies for CVE-2021-38538 require immediate firmware updates from NETGEAR, as the vendor has released patches addressing the stored XSS vulnerability in all affected model versions. Organizations should implement network segmentation to isolate critical infrastructure from potentially compromised devices, while also establishing monitoring protocols to detect unauthorized access attempts to router management interfaces. Network administrators should enforce strong authentication mechanisms, including multi-factor authentication where possible, and regularly audit router configurations for unauthorized changes. The vulnerability demonstrates the importance of maintaining up-to-date firmware across all network equipment, as highlighted in NIST SP 800-128 guidelines for secure network device management. Additionally, implementing web application firewalls and content security policies can provide additional defense-in-depth measures to prevent exploitation of similar vulnerabilities in the future, particularly for devices that may not receive timely vendor updates.