CVE-2018-17016 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 reboot_timer name.
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Analysis
by VulDB Data Team • 03/23/2020
The vulnerability CVE-2018-17016 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 enables authenticated attackers to disrupt router services through malformed JSON data. This issue stems from inadequate input validation mechanisms within the router's web interface and service management components, specifically impacting the reboot_timer functionality where the system fails to properly handle excessively long JSON payloads. The vulnerability manifests when an authenticated user submits malformed JSON data to the reboot_timer parameter, causing the affected services including inetd, HTTP, DNS, and UPnP to become unresponsive or crash entirely.
The technical implementation of this vulnerability aligns with CWE-129, Input Validation, and CWE-772, Missing Release of Resource after Effective Lifetime, as the router fails to properly validate or sanitize input data before processing it within critical system services. The flaw operates at the application layer where JSON parsing routines lack proper bounds checking, allowing attackers to craft malicious payloads that exceed buffer limits and cause service termination. This represents a classic buffer overflow condition that affects the router's service management infrastructure, specifically targeting the reboot_timer configuration parameter which is used to schedule system reboots. The vulnerability demonstrates poor defensive programming practices and inadequate error handling mechanisms that fail to account for malformed input scenarios.
From an operational perspective, this vulnerability presents significant impact to network infrastructure security as it allows authenticated attackers to cause denial of service conditions across multiple critical router services. The crash of inetd service affects the router's ability to handle incoming network connections, while HTTP service disruption prevents web-based management access, DNS service failure impacts local network name resolution, and UPnP service crashes compromise device discovery and port mapping functionality. This multi-service disruption creates cascading effects that can render the entire router unusable for network operations, potentially affecting all connected devices and network communications. The vulnerability is particularly concerning because it requires only authenticated access, meaning that attackers who have gained credentials to the router's administrative interface can immediately exploit this weakness to cause service disruptions.
The attack vector for this vulnerability follows ATT&CK technique T1072, Software Deployment Tools, as attackers can leverage legitimate administrative access to submit malicious JSON payloads through the router's web interface. The exploitation process involves authenticating to the router's management interface and then navigating to the reboot_timer configuration settings, where the attacker submits oversized JSON data to trigger the service crashes. This vulnerability also maps to ATT&CK technique T1499, Endpoint Denial of Service, as it directly targets the availability of critical endpoint services. Organizations should consider implementing network segmentation to limit access to administrative interfaces and deploy monitoring solutions to detect anomalous JSON data submissions. The vulnerability highlights the importance of input sanitization and proper bounds checking in embedded systems, particularly those handling user-provided configuration data. Mitigation strategies should include firmware updates from TP-Link, implementation of network access controls, and regular security assessments of network infrastructure devices to identify similar input validation weaknesses.