CVE-2018-21203 in R6100
Summary
by MITRE
Certain NETGEAR devices are affected by a stack-based buffer overflow by an unauthenticated attacker. This affects R6100 before 1.0.1.20, R9000 before 1.0.2.52, WNDR3700v4 before 1.0.2.96, WNDR4300 before 1.0.2.98, WNDR4300v2 before 1.0.0.50, and WNDR4500v3 before 1.0.0.50.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 06/03/2024
This vulnerability represents a critical stack-based buffer overflow flaw that affects multiple NETGEAR router models including the R6100, R9000, and various WNDR series devices. The flaw exists in the web interface handling of HTTP requests, specifically when processing certain parameters in the URL or POST data. An unauthenticated attacker can exploit this vulnerability by sending a specially crafted HTTP request that exceeds the allocated buffer space on the device's stack memory. The vulnerability is classified under CWE-121 Stack-based Buffer Overflow, which occurs when a program writes data beyond the bounds of a fixed-length buffer allocated on the stack. This type of vulnerability is particularly dangerous because it can lead to arbitrary code execution, system crashes, or complete device compromise without requiring any authentication credentials.
The technical implementation of this vulnerability involves the device's web server component failing to properly validate input lengths before copying data into fixed-size buffers. When an attacker sends a malformed HTTP request containing excessive data in specific parameters, the buffer overflow occurs during the parsing process, potentially overwriting adjacent memory locations including return addresses and function pointers. This allows an attacker to manipulate the execution flow of the web server process and execute malicious code with the privileges of the web server. The vulnerability affects a range of NETGEAR routers released prior to specific firmware versions, indicating that this was a widespread issue across multiple product lines. The attack surface is particularly concerning because it operates at the network level and does not require any authentication, making it accessible to anyone who can reach the device's IP address.
The operational impact of this vulnerability extends beyond simple device compromise to potentially enable broader network infiltration and persistent access. An attacker who successfully exploits this vulnerability could gain complete control over the affected router, allowing them to modify network configurations, redirect traffic through malicious servers, or establish persistent backdoors. The vulnerability also creates potential for denial-of-service conditions where the device becomes unstable and unusable. From an attacker perspective, this vulnerability aligns with ATT&CK technique T1021.001 for Remote Services and T1059.007 for Command and Scripting Interpreter, as it enables remote code execution and command execution capabilities. The affected devices typically operate in home or small office environments where network monitoring is minimal, making such exploitation particularly dangerous.
Mitigation strategies for this vulnerability primarily involve updating to the latest firmware versions provided by NETGEAR, which contain patches that properly validate input lengths and prevent buffer overflows. Network administrators should also implement network segmentation and access controls to limit exposure, particularly by restricting direct internet access to router management interfaces. Additional protective measures include monitoring network traffic for suspicious patterns and implementing intrusion detection systems that can identify malformed HTTP requests targeting known vulnerable parameters. The vulnerability demonstrates the importance of secure coding practices and input validation, particularly in network-facing applications. Organizations should also consider implementing network access control lists to restrict access to administrative interfaces and regularly audit their network infrastructure for similar vulnerabilities. This case highlights the critical need for regular firmware updates and vulnerability assessments, especially for network infrastructure devices that are often overlooked in security monitoring programs.