CVE-2023-36355 in TL-WR940N
Summary
by MITRE • 06/22/2023
TP-Link TL-WR940N V4 was discovered to contain a buffer overflow via the ipStart parameter at /userRpm/WanDynamicIpV6CfgRpm. This vulnerability allows attackers to cause a Denial of Service (DoS) via a crafted GET request.
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Analysis
by VulDB Data Team • 06/24/2024
The vulnerability identified as CVE-2023-36355 affects TP-Link TL-WR940N V4 routers and represents a critical buffer overflow condition within the web interface configuration handling. This issue manifests in the /userRpm/WanDynamicIpV6CfgRpm page where the ipStart parameter fails to properly validate input length, creating an exploitable condition that can be leveraged by remote attackers to disrupt service availability. The vulnerability stems from inadequate bounds checking in the router's web server implementation, specifically when processing dynamic IPv6 configuration parameters through the web management interface.
The technical flaw occurs when the router's web server processes a GET request containing an excessively long ipStart parameter value. Without proper input validation or buffer size limitations, the system allocates insufficient memory space for the parameter handling routine, leading to memory corruption when the oversized input is processed. This buffer overflow condition directly results in a denial of service scenario where the router's web interface becomes unresponsive or crashes entirely, preventing legitimate administrative access to the device configuration. The vulnerability is classified under CWE-121 as a stack-based buffer overflow, representing a fundamental memory safety issue that has been consistently identified as a high-risk security flaw in embedded systems.
The operational impact of this vulnerability extends beyond simple service disruption, as it provides attackers with a reliable method to render network infrastructure devices unusable without requiring authentication or specialized access privileges. The DoS condition affects the router's ability to provide network connectivity through its WAN interface, potentially isolating connected networks from external communication while leaving the device completely inaccessible for legitimate configuration changes. Attackers can exploit this vulnerability through simple web requests, making it particularly dangerous as it requires minimal technical expertise and can be automated at scale. This vulnerability directly maps to attack techniques described in the MITRE ATT&CK framework under T1499.004 for network denial of service attacks, where adversaries leverage software vulnerabilities to compromise system availability.
Mitigation strategies for CVE-2023-36355 should prioritize immediate firmware updates from TP-Link to address the underlying buffer overflow condition in the web interface handling code. Network administrators should implement network segmentation and access controls to limit exposure of affected devices to untrusted networks, while also monitoring for anomalous traffic patterns that might indicate exploitation attempts. The vulnerability highlights the importance of input validation in embedded web servers and demonstrates the necessity of robust security testing for network infrastructure devices. Organizations should consider implementing network-based intrusion detection systems to monitor for crafted GET requests containing oversized parameters, and establish procedures for regular firmware updates to address known vulnerabilities in network equipment. Additionally, the affected devices should be configured with minimal web interface functionality and restricted access to reduce the attack surface available to potential exploiters.