CVE-2018-17015 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 ddns phddns username.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 03/23/2020
The vulnerability CVE-2018-17015 represents a critical buffer overflow condition affecting TP-Link TL-WR886N routers running specific firmware versions. This issue stems from inadequate input validation within the device's dynamic domain name system implementation, specifically when processing ddns phddns username parameters. The flaw exists in the router's handling of JSON data structures, where the system fails to properly sanitize or limit the length of incoming data before processing it through the inetd service. This vulnerability impacts multiple network services including HTTP, DNS, and UPnP protocols, creating a cascading effect that can bring down essential router functionalities. The authentication requirement means that an attacker must first establish valid credentials to exploit this weakness, though this presents a significant risk as it allows for service disruption attacks against legitimate users.
The technical exploitation of this vulnerability occurs when an authenticated user submits maliciously crafted JSON data containing an excessively long username parameter to the ddns phddns functionality. This excessive data length causes a buffer overflow condition within the router's memory management, leading to service crashes and potential system instability. The vulnerability demonstrates characteristics consistent with CWE-121, which describes stack-based buffer overflow conditions, and CWE-122, which addresses heap-based buffer overflows. The router's inability to properly validate input length creates a path for attackers to disrupt network services, effectively creating a denial-of-service condition that can render the router's internet connectivity and local network access unreliable. The impact extends beyond simple service interruption as the affected services include inetd, which serves as the internet super daemon responsible for managing various network services, making this a particularly dangerous vulnerability for network infrastructure.
The operational impact of CVE-2018-17015 significantly affects network availability and reliability for users of affected TP-Link devices. When exploited, the vulnerability can cause complete service outages across multiple router functions, forcing users to manually restart their devices or potentially requiring firmware updates to restore normal operations. This disruption affects not only internet connectivity but also local network services, as the UPnP protocol and DNS resolution services become unavailable. The vulnerability's presence in both version 6.0 2.3.4 and 7.0 1.1.0 firmware releases indicates a persistent flaw that was not adequately addressed in the device's security implementation. From an attacker's perspective, this vulnerability aligns with ATT&CK technique T1499.004, which covers network disruption attacks, and represents a medium to high severity threat that can be exploited to create service availability issues. The impact is particularly concerning for home and small office networks where router reliability is crucial for maintaining connectivity.
Mitigation strategies for CVE-2018-17015 should prioritize immediate firmware updates from TP-Link to address the underlying buffer overflow condition. Network administrators should implement strict input validation measures and monitor router services for unusual behavior patterns that might indicate exploitation attempts. The vulnerability highlights the importance of proper input sanitization and length validation in embedded systems, particularly those handling JSON data structures. Organizations should also consider implementing network segmentation and monitoring to detect potential exploitation attempts, as well as establishing regular firmware update schedules to ensure devices remain protected against known vulnerabilities. The security community should also consider this vulnerability as a prime example of why embedded systems require robust memory management and input validation controls to prevent exploitation of buffer overflow conditions that can lead to complete service disruption.