CVE-2018-17017 in TL-WR886N
Summary
by MITRE
An issue was discovered on TP-Link TL-WR886N 6.0 2.3.4 and TL-WR886N 7.0 1.1.0 devices. Authenticated attackers can crash router services (e.g., inetd, HTTP, DNS, and UPnP) via long JSON data for dhcpd udhcpd enable.
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Analysis
by VulDB Data Team • 03/23/2020
The vulnerability CVE-2018-17017 affects TP-Link TL-WR886N routers running firmware versions 6.0 2.3.4 and 7.0 1.1.0, representing a critical security flaw that allows authenticated attackers to cause service disruptions on affected devices. This issue manifests through the manipulation of JSON data parameters within the dhcpd udhcpd enable functionality, demonstrating a classic buffer overflow or input validation vulnerability that can be exploited by users with legitimate access credentials to the router's administrative interface.
The technical flaw stems from inadequate input sanitization and boundary checking within the router's firmware implementation, specifically in how it processes JSON data for the udhcpd service configuration. When an authenticated user submits excessively long JSON data to the dhcpd udhcpd enable parameter, the system fails to properly validate the input length or structure, leading to memory corruption that ultimately results in service crashes. This vulnerability operates at the application layer and affects core network services including inetd, HTTP, DNS, and UPnP protocols that are essential for router functionality and network connectivity. The issue falls under CWE-121, which describes buffer overflow conditions where insufficient space allocation leads to memory corruption, and may also align with CWE-122 for heap-based buffer overflows that occur when insufficient memory is allocated for data processing.
The operational impact of this vulnerability extends beyond simple service disruption, as it can effectively render the affected router unusable for network operations. When critical services such as HTTP (web interface), DNS (domain name resolution), UPnP (universal plug and play), and inetd (internet super server) crash, users lose access to router management capabilities and network connectivity. This creates a denial of service condition that can persist until manual intervention occurs, requiring router reboot or firmware reinstallation to restore normal operations. The vulnerability is particularly concerning because it requires only authenticated access to the router's administrative interface, meaning that any user with legitimate login credentials could exploit this flaw to cause service disruption. This aligns with ATT&CK technique T1499.001 for network denial of service attacks, where adversaries leverage legitimate access to cause service unavailability.
Mitigation strategies for CVE-2018-17017 should prioritize immediate firmware updates from TP-Link, as the vendor would have released patches addressing the input validation issues in subsequent firmware versions. Network administrators should also implement access control measures to limit administrative privileges to only trusted users and establish monitoring protocols to detect unusual service disruptions that might indicate exploitation attempts. Additional defensive measures include implementing network segmentation to isolate critical services, deploying intrusion detection systems to monitor for anomalous JSON data patterns, and establishing regular vulnerability scanning procedures to identify potentially affected devices within the network infrastructure. The vulnerability highlights the importance of robust input validation and proper boundary checking in embedded systems, particularly in network infrastructure devices where service availability is critical for network operations and user productivity.