CVE-2018-17014 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 ip_mac_bind name.
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Analysis
by VulDB Data Team • 03/23/2020
The vulnerability identified as CVE-2018-17014 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 crafted JSON data manipulation. This issue specifically targets the ip_mac_bind functionality within the router's configuration interface, where the device fails to properly validate input length when processing JSON data structures. The vulnerability stems from inadequate bounds checking mechanisms within the router's web management interface, allowing maliciously constructed JSON payloads to trigger buffer overflow conditions or memory corruption states that ultimately result in service crashes. The affected services include inetd, HTTP server, DNS resolver, and UPnP daemon, which are fundamental components that maintain network connectivity and device functionality. This flaw operates at the application layer and represents a classic example of improper input validation that can lead to denial of service conditions, effectively compromising the availability of network services provided by the device.
The technical implementation of this vulnerability involves the exploitation of a buffer overflow condition within the router's JSON parsing routines, where the ip_mac_bind parameter name field receives excessive input length without proper sanitization. According to CWE classification, this corresponds to CWE-121: Stack-based Buffer Overflow, as the malicious JSON data causes stack memory corruption when processed by the affected router services. The attack vector requires an authenticated session, meaning that an adversary must first obtain valid credentials to access the router's management interface before executing the exploit. This authentication requirement reduces the attack surface compared to unauthenticated vulnerabilities but does not eliminate the severity of impact, particularly in environments where router administrative credentials are weak or compromised. The vulnerability demonstrates characteristics consistent with ATT&CK technique T1499.002: Network Denial of Service, where an attacker targets network infrastructure to disrupt service availability. The router's failure to implement proper input length validation creates a condition where legitimate service operations are interrupted through malicious input manipulation.
The operational impact of CVE-2018-17014 extends beyond simple service disruption, potentially creating extended network outages that affect multiple connected devices and applications dependent on the router's functionality. When the inetd service crashes, it can prevent remote access to the device, while HTTP server failures block web-based management access, DNS service disruptions can cause internet connectivity issues for all connected devices, and UPnP daemon crashes may prevent automatic port forwarding configurations from working properly. The cascading effect of these service failures can result in complete network isolation for users within the affected subnet, particularly in small office or home environments where the router serves as the primary network gateway. The vulnerability's exploitation can be automated through scripting tools that generate the appropriate JSON payloads, making it particularly dangerous as a persistent threat that can be repeatedly leveraged by attackers with valid credentials. Organizations relying on these devices for network infrastructure may experience extended downtime during incident response activities, as the affected services require manual restart or device reboot to restore normal operations.
Mitigation strategies for CVE-2018-17014 should prioritize firmware updates from TP-Link, as the vendor has likely released patches addressing the buffer overflow conditions in subsequent firmware versions. Network administrators should implement strict access controls limiting administrative privileges to only authorized personnel and enforce strong authentication mechanisms including multi-factor authentication where possible. Monitoring systems should be configured to detect unusual service restart patterns or authentication attempts that could indicate exploitation attempts. Network segmentation techniques can help isolate vulnerable devices from critical infrastructure, reducing the potential impact of successful exploitation. Additionally, implementing network-based intrusion detection systems can help identify malformed JSON traffic patterns that may indicate attempts to exploit this vulnerability. Regular vulnerability scanning of network infrastructure should include checks for this specific CVE, and device inventory management should track firmware versions to ensure all affected TP-Link routers are updated. The vulnerability highlights the importance of secure coding practices in embedded systems and demonstrates how seemingly minor input validation flaws can create significant operational disruptions in network infrastructure devices. Organizations should also consider implementing network access control lists to restrict administrative access to router management interfaces from trusted network segments only, reducing the attack surface for authenticated exploitation attempts.