CVE-2018-20372 in TD-W8961ND
Summary
by MITRE
TP-Link TD-W8961ND devices allow XSS via the hostname of a DHCP client.
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Analysis
by VulDB Data Team • 04/23/2020
The CVE-2018-20372 vulnerability affects TP-Link TD-W8961ND wireless routers, representing a cross-site scripting flaw that emerges through the device's handling of DHCP client hostnames. This vulnerability resides within the web-based administrative interface of the router, where user-provided input from DHCP client hostnames is inadequately sanitized before being rendered back to users. The affected device operates under the assumption that all input from network clients is trustworthy, failing to implement proper input validation and output encoding mechanisms. This oversight creates a pathway for malicious actors to inject malicious scripts into the router's web interface, potentially compromising the device's security and the network it protects. The vulnerability specifically targets the hostname field used in DHCP client listings, where an attacker can craft a malicious hostname containing script code that executes when other users view the DHCP client list within the router's administrative web interface.
The technical exploitation of this vulnerability involves crafting a DHCP client hostname containing malicious JavaScript code that gets executed in the context of the web browser accessing the router's administrative interface. When the router displays the DHCP client information, the malicious hostname gets rendered without proper sanitization, allowing the injected script to execute in the browser's context. This type of vulnerability falls under the CWE-79 category of Cross-Site Scripting, specifically representing a reflected XSS attack where the malicious payload is reflected back to the user through the router's web interface. The attack vector requires minimal privileges since the vulnerability exists in the web interface that may be accessible to authenticated users or even unauthenticated users depending on the router's configuration. The vulnerability's impact is amplified by the fact that routers serve as central network control points, making successful exploitation potentially devastating for network security.
The operational impact of CVE-2018-20372 extends beyond simple script execution, as it provides attackers with potential access to sensitive administrative functions within the router's web interface. Successful exploitation could allow attackers to modify router settings, change administrative passwords, or even redirect traffic through the compromised device. This vulnerability represents a significant risk to network integrity since the router acts as a gateway device, and compromise of its administrative interface could lead to complete network takeover. The attack scenario typically involves an attacker either physically placing a device on the network or using network reconnaissance to identify the router's presence and then crafting malicious DHCP responses. The vulnerability's persistence is particularly concerning as the malicious hostname remains in the DHCP client list until manually cleared, potentially affecting multiple users who access the router's web interface. Network administrators may not immediately detect this type of attack since it operates through legitimate network protocols and appears as normal DHCP client activity.
Mitigation strategies for CVE-2018-20372 should focus on both immediate defensive measures and long-term architectural improvements. The most effective immediate solution involves applying the vendor-provided firmware update that addresses the input sanitization issue in the web interface. Network administrators should also implement network segmentation to isolate critical systems from potentially compromised devices, reducing the attack surface. Additional defensive measures include disabling unnecessary web administration access, implementing strong authentication mechanisms, and monitoring DHCP client activity for suspicious hostnames. Security monitoring should include inspection of DHCP responses for potentially malicious content, particularly in environments where the network is not fully trusted. The vulnerability highlights the importance of input validation and output encoding practices, aligning with ATT&CK technique T1059.007 for script injection attacks. Organizations should also consider implementing network access control measures and regular security assessments to identify similar vulnerabilities in other network devices. The incident underscores the necessity of following secure coding practices and implementing proper input validation for all user-supplied data, particularly in web-based administrative interfaces where such vulnerabilities can have far-reaching consequences for network security.