CVE-2018-17018 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 time_switch name.
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Analysis
by VulDB Data Team • 03/23/2020
The vulnerability CVE-2018-17018 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 essential router services through malformed JSON data. This issue manifests when attackers exploit a buffer overflow condition in the time_switch name parameter processing within the router's web interface, specifically targeting the inetd service and other network services such as HTTP, DNS, and UPnP. The vulnerability stems from inadequate input validation and bounds checking mechanisms within the router's firmware implementation, allowing attackers with valid credentials to craft malicious JSON payloads that exceed allocated memory buffers.
The technical exploitation of this vulnerability involves sending specially crafted JSON data containing an excessively long time_switch name parameter to the router's configuration interface. This malformed input triggers a buffer overflow condition that causes the targeted services to terminate unexpectedly, resulting in a denial of service scenario that disrupts network connectivity and router functionality. The affected services include inetd which manages network services, HTTP servers for web interface access, DNS services for domain name resolution, and UPnP for network device discovery and communication. The vulnerability's classification aligns with CWE-121 Stack-based Buffer Overflow, as the issue occurs in stack memory allocation during JSON parameter processing, and the exploitation technique maps to ATT&CK tactic TA0040 (Defense Evasion) and technique T1499.004 (Endpoint Denial of Service) through service disruption methods.
The operational impact of CVE-2018-17018 extends beyond simple service disruption, as it compromises the reliability and availability of network infrastructure that many users depend upon for internet connectivity. Network administrators face potential service interruptions that can affect multiple users simultaneously, particularly in residential or small office environments where these routers serve as primary network gateways. The vulnerability's authenticated nature means that attackers must first obtain valid user credentials, typically through social engineering, credential reuse, or other initial compromise techniques, making it more difficult to exploit but still highly dangerous in environments where router access credentials are weak or compromised. Organizations and individuals using these specific router models should consider the broader implications for network security, as service disruption can lead to cascading failures in dependent systems and applications.
Mitigation strategies for CVE-2018-17018 should prioritize firmware updates from TP-Link, as the vendor has likely released patches addressing the buffer overflow condition in subsequent firmware versions. Network administrators should also implement access controls to limit router management interface access to trusted users only, employ strong authentication mechanisms, and regularly audit router configurations for unauthorized changes. Additional defensive measures include monitoring network traffic for suspicious JSON payloads, implementing network segmentation to limit the impact of potential exploitation, and establishing incident response procedures for handling service disruption events. The vulnerability demonstrates the importance of proper input validation in embedded systems and highlights the need for manufacturers to conduct thorough security testing of firmware components, particularly those handling user-supplied data in network services. Organizations should also consider the broader implications of using legacy or unsupported router firmware versions, as these devices may contain multiple unpatched vulnerabilities that could be exploited in combination to achieve more severe security impacts.