CVE-2018-21155 in D7800
Summary
by MITRE
Certain NETGEAR devices are affected by stored XSS. This affects D7800 before 1.0.1.34, DM200 before 1.0.0.52, R6100 before 1.0.1.22, R7500 before 1.0.0.122, R7500v2 before 1.0.3.26, R7800 before 1.0.2.42, R8900 before 1.0.4.2, R9000 before 1.0.3.16, WNDR4300 before 1.0.2.98, WNDR4300v2 before 1.0.0.54, WNDR4500v3 before 1.0.0.54, and WNR2000v5 before 1.0.0.64.
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Analysis
by VulDB Data Team • 05/06/2025
The vulnerability identified as CVE-2018-21155 represents a critical stored cross-site scripting flaw affecting multiple NETGEAR router models across various product lines. This security weakness resides in the web-based management interface of affected devices, allowing attackers to inject malicious scripts that persist within the device's configuration storage. The vulnerability impacts a wide range of NETGEAR routers including the D7800, DM200, R6100, R7500 series, R7800, R8900, R9000, WNDR4300 series, WNDR4500v3, and WNR2000v5 models. The affected firmware versions demonstrate that this issue has persisted across multiple generations of devices, suggesting a fundamental flaw in the input validation and output encoding mechanisms within the web interface components. This stored XSS vulnerability operates by allowing malicious code to be stored on the device and subsequently executed whenever users access the affected management interface, creating a persistent threat vector that can compromise user sessions and potentially escalate privileges.
The technical exploitation of this vulnerability occurs through the manipulation of input fields within the router's web administration interface where user-supplied data is not properly sanitized or encoded before being stored and later rendered to web browsers. Attackers can craft malicious payloads that target the router's web interface, embedding scripts that execute in the context of authenticated users accessing the device management pages. The stored nature of this vulnerability means that once injected, the malicious code remains persistent on the device and executes every time the affected interface is accessed, making it particularly dangerous for network administrators who may unknowingly execute compromised scripts while performing routine maintenance tasks. This flaw falls under CWE-79 which specifically addresses Cross-Site Scripting vulnerabilities, and more precisely aligns with CWE-807 which covers "Reliance on Untrusted Inputs in a Security Decision." The vulnerability's impact extends beyond simple script execution as it can potentially enable session hijacking, data exfiltration, and privilege escalation attacks against the router's management interface.
The operational impact of CVE-2018-21155 is significant for network administrators and organizations relying on affected NETGEAR devices, as the stored XSS vulnerability creates persistent security risks that can compromise network security infrastructure. When exploited, this vulnerability allows attackers to execute arbitrary code within the context of the router's web interface, potentially enabling them to gain unauthorized access to network configurations, modify device settings, or establish persistent backdoors. The threat landscape for this vulnerability is particularly concerning because it affects consumer-grade and small business routers that often serve as primary network gateways, making them attractive targets for attackers seeking to establish persistent access to network infrastructure. Network administrators may be unaware of the compromise until significant damage has occurred, as the malicious scripts execute silently when administrators access the device management interface. This vulnerability also aligns with ATT&CK technique T1071.004 which covers Application Layer Protocol: DNS, as compromised routers could potentially be used to redirect DNS queries or facilitate further attacks on network traffic.
The mitigation strategies for this vulnerability primarily involve firmware updates provided by NETGEAR to address the stored XSS implementation flaws in affected devices. Organizations should immediately update all affected router models to the latest available firmware versions that contain patches for this vulnerability, with the specific version numbers indicating the minimum required firmware versions for each affected model. Network segmentation and access controls should be implemented to limit direct access to router management interfaces, particularly restricting access to trusted administrative networks. Additional defensive measures include implementing network monitoring to detect unusual traffic patterns that might indicate exploitation attempts, and conducting regular security assessments of network infrastructure to identify potentially compromised devices. Security awareness training for network administrators is crucial to ensure they understand the risks associated with accessing potentially compromised management interfaces and the importance of maintaining updated firmware across all network devices. The vulnerability also highlights the importance of secure coding practices and input validation in web applications, particularly for network infrastructure devices that must handle user input through web interfaces. Organizations should establish robust patch management procedures to ensure timely deployment of security updates across all network equipment, as this vulnerability demonstrates how long-standing flaws can persist across multiple firmware versions without proper remediation.