CVE-2018-18489 in TL-WR840N v2
Summary
by MITRE
The ping feature in the Diagnostic functionality on TP-LINK WR840N v2 Firmware 3.16.9 Build 150701 Rel.51516n devices allows remote attackers to cause a denial of service (HTTP service termination) by modifying the packet size to be higher than the UI limit of 1472.
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Analysis
by VulDB Data Team • 08/29/2023
The vulnerability identified as CVE-2018-18489 resides within the diagnostic functionality of TP-LINK WR840N v2 routers running firmware version 3.16.9 Build 150701 Rel.51516n. This issue specifically affects the ping feature implementation which is part of the router's diagnostic tools accessible through the web interface. The affected device operates under the assumption that user input through the web UI will remain within reasonable bounds, creating a gap in input validation and sanitization. This vulnerability represents a classic example of insufficient input validation as classified under CWE-20, where the system fails to properly validate or sanitize user-supplied data before processing it.
The technical flaw manifests when attackers manipulate the packet size parameter in the ping functionality beyond the UI-imposed limit of 1472 bytes. While the web interface may visually constrain users to this limit, the underlying processing logic does not adequately validate the actual data being transmitted to the device's backend services. This discrepancy creates an opportunity for remote attackers to send malformed packets that exceed expected parameters, leading to unexpected behavior in the router's processing mechanisms. The vulnerability operates at the application layer where HTTP service termination occurs, indicating that the device's web server or diagnostic service becomes unresponsive due to the malformed input causing a resource exhaustion or memory corruption scenario.
The operational impact of this vulnerability is significant as it enables remote attackers to perform denial of service attacks against the affected routers. When successfully exploited, the HTTP service termination means that legitimate users lose access to the router's web management interface, effectively rendering the device administratively inaccessible. This creates a persistent availability issue that requires manual intervention to restore service, typically involving a device reboot or firmware reinstallation. The attack vector is particularly concerning because it requires no authentication, making it accessible to anyone with network access to the device, and the impact is immediate and disruptive to network operations.
Mitigation strategies for this vulnerability should focus on implementing proper input validation and sanitization measures within the diagnostic functionality. Network administrators should prioritize firmware updates from TP-LINK to address this specific issue, as the vendor has likely released patches to correct the input validation weakness. Additionally, implementing network segmentation and access controls can help limit exposure by restricting direct access to the router's management interface from untrusted networks. The vulnerability demonstrates the importance of defensive programming practices and proper parameter validation as outlined in the OWASP Top Ten and MITRE ATT&CK framework's defense evasion techniques, where such input validation failures can lead to service disruption and unauthorized access to network infrastructure.