CVE-2018-21135 in R6700
Summary
by MITRE
Certain NETGEAR devices are affected by a stack-based buffer overflow by an authenticated user. This affects R6700 before 1.0.1.48, R7500 before 1.0.0.124, R7800 before 1.0.2.58, R8900 before 1.0.4.2, R9000 before 1.0.4.2, WNDR3700v4 before 1.0.2.102, WNDR4300v1 before 1.0.2.104, WNDR4300v2 before 1.0.0.56, WNDR4500v3 before 1.0.0.56, and WNR2000v5-R2000 before 1.0.0.68.
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Analysis
by VulDB Data Team • 06/02/2024
This vulnerability represents a critical stack-based buffer overflow flaw in NETGEAR router firmware that can be exploited by authenticated users with local access to the device. The issue stems from improper input validation within the web interface authentication handling mechanisms, specifically affecting multiple models within the R6700, R7500, R7800, R8900, R9000, WNDR3700v4, WNDR4300v1, WNDR4300v2, WNDR4500v3, and WNR2000v5-R2000 device families. The vulnerability is categorized under CWE-121 Stack-based Buffer Overflow, which falls within the broader category of memory safety issues that have been consistently identified as high-risk in cybersecurity assessments. This flaw allows an authenticated attacker to manipulate memory layout through crafted input parameters, potentially leading to arbitrary code execution within the device's operating environment.
The technical exploitation of this vulnerability requires an attacker to have valid login credentials for the affected router, typically through legitimate user accounts or administrative access. Once authenticated, the attacker can submit malicious input through web interface forms or API endpoints that process user-supplied data without proper bounds checking. The buffer overflow occurs when the firmware fails to validate the length of input data before copying it into a fixed-size stack buffer, allowing the attacker to overwrite adjacent memory locations including return addresses and control registers. This type of vulnerability is particularly dangerous in network infrastructure devices because it can be leveraged to gain persistent access to network traffic, modify routing configurations, or establish backdoor access points. The ATT&CK framework categorizes this as a privilege escalation technique under T1068, where an attacker leverages existing credentials to execute malicious code with elevated privileges.
The operational impact of this vulnerability extends beyond simple code execution, as it enables attackers to compromise entire network infrastructures through lateral movement and persistent access. Network administrators who rely on these devices for core routing functions face significant risk of unauthorized network access, data interception, and potential use as pivot points for attacking internal network segments. The vulnerability affects devices running firmware versions prior to the specified patches, making it particularly concerning for organizations with legacy deployments or devices that have not been updated. Attackers can exploit this flaw to gain root-level access to the router's operating system, potentially enabling them to modify firewall rules, redirect traffic through malicious proxies, or install persistent malware that survives device reboots. The vulnerability's presence in multiple router models suggests a systemic issue within NETGEAR's firmware development practices, indicating potential gaps in code review and security testing processes.
Organizations should immediately implement firmware updates for all affected devices, ensuring that administrators verify the correct patch versions are applied to each specific model. Network segmentation strategies should be enhanced to limit the potential impact of compromised devices, while monitoring systems should be configured to detect unusual authentication patterns or unauthorized configuration changes. Security teams should consider implementing additional access controls such as multi-factor authentication and regular credential rotation to reduce the likelihood of successful exploitation. The vulnerability highlights the importance of maintaining up-to-date firmware across all network infrastructure components and demonstrates the critical need for comprehensive vulnerability management programs that include regular security assessments and penetration testing of network devices. Device vendors should be encouraged to implement more robust input validation mechanisms and automated security testing in their development lifecycle to prevent similar issues from arising in future firmware releases.