CVE-2023-40478 in RAX30
Summary
by MITRE • 05/03/2024
NETGEAR RAX30 Telnet CLI passwd Stack-based Buffer Overflow Remote Code Execution Vulnerability. This vulnerability allows network-adjacent attackers to execute arbitrary code on affected installations of NETGEAR RAX30 routers. Although authentication is required to exploit this vulnerability, the existing authentication mechanism can be bypassed.
The specific flaw exists within the telnet CLI service, which listens on TCP port 23. The issue results from the lack of proper validation of the length of user-supplied data prior to copying it to a fixed-length stack-based buffer. An attacker can leverage this vulnerability to execute code in the context of root. Was ZDI-CAN-20009.
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Analysis
by VulDB Data Team • 01/03/2025
The CVE-2023-40478 vulnerability represents a critical stack-based buffer overflow flaw in the telnet CLI service of NETGEAR RAX30 routers, classified under CWE-121 Stack-based Buffer Overflow. This vulnerability exists within the network-adjacent attack surface where an attacker can exploit the lack of input validation in the telnet command line interface that operates on TCP port 23. The flaw specifically manifests when user-supplied data is copied to a fixed-length stack buffer without proper length verification, creating a condition where excessive input can overwrite adjacent memory locations. The vulnerability's severity is amplified by the fact that while authentication is typically required, the existing authentication mechanism can be bypassed, reducing the attack barrier significantly. This allows adversaries to potentially gain unauthorized access to the router's command execution environment, which operates with root privileges due to the nature of the telnet service implementation. The vulnerability directly maps to ATT&CK technique T1210 Exploitation of Remote Services, as it leverages a network service to achieve code execution in the highest privilege context available on the device.
The technical exploitation of this vulnerability requires careful crafting of input data that exceeds the allocated stack buffer size, typically through the telnet CLI interface. Attackers can construct malicious payloads that overwrite return addresses and control registers, effectively hijacking the execution flow of the telnet service. The stack-based nature of the buffer overflow means that the memory layout is predictable, making exploitation more feasible for skilled attackers who can leverage the existing authentication bypass mechanism. The vulnerability's impact extends beyond simple code execution as it provides an attacker with root-level access to the router's operating system, enabling complete compromise of the device and potentially broader network access. The fact that this vulnerability affects the telnet CLI service indicates that the device's security posture is weakened by the presence of legacy services that should have been deprecated in favor of more secure protocols like SSH. This aligns with ATT&CK technique T1059 Command and Scripting Interpreter where attackers can execute commands through compromised services. The vulnerability's existence in a consumer-grade router demonstrates how embedded device security often lags behind enterprise security practices, creating persistent attack vectors that remain unpatched for extended periods.
The operational impact of CVE-2023-40478 extends beyond individual device compromise to potentially enable large-scale network infiltration when multiple devices are affected. Once an attacker gains root access to a router through this vulnerability, they can modify routing tables, intercept traffic, establish backdoors, or use the compromised device as a pivot point for attacking other network segments. The telnet service's presence on TCP port 23 makes it particularly attractive to automated scanning tools, increasing the likelihood of exploitation. The authentication bypass capability significantly increases the attack surface, as it removes the requirement for valid credentials, making this vulnerability particularly dangerous in environments where network segmentation is not properly implemented. The vulnerability's classification as a remote code execution flaw means that attackers do not need physical access to the device, enabling attacks from any network location that can reach the router's telnet service. This vulnerability directly impacts the CIA triad by compromising confidentiality through potential traffic interception, integrity through possible configuration changes, and availability through potential denial of service attacks. The fact that this vulnerability was identified as ZDI-CAN-20009 indicates it was reported to a security vendor before public disclosure, highlighting the importance of coordinated vulnerability disclosure processes. Organizations should consider implementing network segmentation to isolate critical devices and monitor for unusual telnet connections on port 23 as part of their defensive strategies.
Mitigation strategies for CVE-2023-40478 should prioritize immediate patching of affected NETGEAR RAX30 devices through official firmware updates from the vendor. Network administrators should disable the telnet service entirely and migrate to SSH-based management protocols where possible, as SSH provides encrypted communication and more robust authentication mechanisms. The implementation of network access controls through firewalls and access control lists should prevent unauthorized access to TCP port 23 from external networks, while internal network segmentation can limit the potential impact of successful exploitation. Regular vulnerability scanning should include detection of running telnet services and other legacy protocols that may expose similar vulnerabilities. The use of intrusion detection systems can help identify suspicious telnet connection attempts and malformed input patterns that may indicate exploitation attempts. Additionally, organizations should implement comprehensive network monitoring to detect unusual routing behavior or traffic patterns that could indicate compromised routers being used as attack platforms. Device hardening practices should include disabling unnecessary services, enforcing strong authentication mechanisms, and regularly auditing device configurations to ensure compliance with security baselines. The vulnerability's nature suggests that similar issues may exist in other NETGEAR devices or firmware versions, making broader security assessments of network infrastructure essential. Organizations should also consider implementing endpoint detection and response solutions that can identify anomalous behavior patterns consistent with exploitation of similar buffer overflow vulnerabilities. The remediation process should include comprehensive testing of firmware updates to ensure that patching does not introduce compatibility issues with existing network configurations, while maintaining detailed logs of all access attempts to affected devices for forensic analysis purposes.