CVE-2018-12692 in TL-WA850RE
Summary
by MITRE
TP-Link TL-WA850RE Wi-Fi Range Extender with hardware version 5 allows remote authenticated users to execute arbitrary commands via shell metacharacters in the wps_setup_pin parameter to /data/wps.setup.json.
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Analysis
by VulDB Data Team • 02/21/2020
The CVE-2018-12692 vulnerability affects TP-Link TL-WA850RE Wi-Fi Range Extender devices with hardware version 5, representing a critical command injection flaw that enables remote authenticated attackers to execute arbitrary system commands. This vulnerability resides within the web-based management interface of the device, specifically in the handling of the wps_setup_pin parameter within the /data/wps.setup.json endpoint. The flaw stems from inadequate input validation and sanitization, allowing attackers who have already established authentication credentials to manipulate the parameter and inject malicious shell metacharacters that get processed by the underlying system shell.
The technical implementation of this vulnerability demonstrates a classic command injection attack vector where the device fails to properly escape or validate user-supplied input before incorporating it into system commands. When an authenticated user submits a crafted wps_setup_pin parameter containing shell metacharacters such as semicolons, ampersands, or other command separators, the system processes these inputs without adequate sanitization, leading to arbitrary command execution with the privileges of the web server process. This represents a CWE-77 vulnerability category, specifically command injection, which is classified as a high-severity issue in the Common Weakness Enumeration catalog.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it provides attackers with complete control over the affected device. Once exploited, malicious actors can execute any command available on the system, potentially leading to unauthorized access to network resources, data exfiltration, or even use of the device as a pivot point for attacking other systems within the local network. The remote nature of the attack means that an authenticated user with access to the device's web interface can perform these operations from anywhere on the network, making the vulnerability particularly dangerous in environments where the device is accessible to multiple users or where credentials might be compromised.
This vulnerability aligns with several tactics outlined in the MITRE ATT&CK framework, particularly focusing on privilege escalation and command execution techniques. The attack chain begins with initial access through legitimate authentication, followed by command injection to escalate privileges and execute arbitrary code. Organizations should consider this vulnerability as part of a broader attack surface assessment, especially in environments where IoT devices are deployed without proper network segmentation or monitoring. The vulnerability underscores the importance of input validation and proper sanitization practices in embedded systems and web applications, as highlighted in industry security standards that emphasize the need for secure coding practices to prevent such injection attacks.
Mitigation strategies for CVE-2018-12692 should include immediate firmware updates from TP-Link, which would address the input validation issues in the affected device. Network segmentation and access controls should be implemented to limit the attack surface, ensuring that only authorized personnel can access the device's management interface. Regular security audits and vulnerability assessments should be conducted to identify similar issues in other networked devices, while monitoring systems should be deployed to detect unusual command execution patterns that might indicate exploitation attempts. Organizations should also consider implementing web application firewalls to provide additional protection against similar injection attacks targeting web interfaces of network devices.