CVE-2014-4728 in WDR4300
Summary
by MITRE
The web server in the TP-LINK N750 Wireless Dual Band Gigabit Router (TL-WDR4300) with firmware before 140916 allows remote attackers to cause a denial of service (crash) via a long header in a GET request.
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Analysis
by VulDB Data Team • 02/20/2022
The TP-LINK N750 Wireless Dual Band Gigabit Router model TL-WDR4300 represents a widely deployed consumer networking device that incorporates web server functionality for administrative access and configuration management. This particular vulnerability affects firmware versions prior to 140916, indicating a specific software regression or implementation flaw that emerged in the device's web server component. The vulnerability manifests as a remote denial of service condition that can be triggered by sending specially crafted HTTP requests to the device's web interface, demonstrating a critical weakness in the router's input validation mechanisms. This issue directly impacts the availability and reliability of the network infrastructure, as unauthorized remote actors can potentially disrupt network services by causing the router to crash and restart.
The technical flaw resides in the web server's handling of HTTP GET requests, specifically when processing header fields that exceed normal length parameters. When a remote attacker crafts a GET request containing an abnormally long header value, the router's web server fails to properly validate or limit the input length, leading to a buffer overflow or memory corruption condition. This type of vulnerability typically falls under CWE-122 Buffer Overflow, where insufficient bounds checking allows malicious input to overwrite adjacent memory regions. The exploitation mechanism is straightforward and requires no authentication, making it particularly dangerous as it can be executed by anyone with network access to the device's web interface. The device's failure to implement proper input sanitization and length validation creates an execution path where malformed headers cause the web server process to terminate unexpectedly, resulting in the complete service disruption.
The operational impact of this vulnerability extends beyond simple service disruption to encompass broader network reliability concerns and potential cascading failures within connected environments. When the router crashes, it becomes inaccessible to legitimate administrators and users, effectively cutting off network connectivity for all devices relying on that particular router for internet access. This denial of service condition can persist until manual intervention occurs or until the device automatically reboots, which may take several minutes. The vulnerability affects all users of affected firmware versions regardless of their network location, as the web server is typically accessible from external networks when port forwarding or remote administration features are enabled. Network administrators face significant challenges in identifying and mitigating this issue, as it can be exploited from anywhere on the internet, and the attack vector does not require sophisticated techniques or deep technical knowledge.
Mitigation strategies for this vulnerability must address both immediate remediation and long-term security posture improvements. The primary and most effective solution involves updating the router's firmware to version 140916 or later, which contains the necessary patches to properly validate and handle HTTP header lengths. Organizations should implement robust firmware update policies and regularly monitor for security advisories from manufacturers, as this vulnerability demonstrates the importance of keeping network infrastructure components current with security patches. Network segmentation and access control measures can provide additional protection by limiting exposure of administrative interfaces to trusted networks only. The implementation of web application firewalls or intrusion prevention systems may help detect and block malformed requests before they reach the vulnerable web server component. From a security framework perspective, this vulnerability aligns with ATT&CK technique T1499.004 Network Denial of Service, where adversaries leverage weaknesses in network infrastructure to disrupt services. The vulnerability also highlights the importance of input validation as a fundamental security control, consistent with NIST SP 800-160 guidance on secure coding practices and the principle of least privilege in network device configuration.