CVE-2020-25786 in DIR-816L
Summary
by MITRE
** UNSUPPORTED WHEN ASSIGNED ** webinc/js/info.php on D-Link DIR-816L 2.06.B09_BETA and DIR-803 1.04.B02 devices allows XSS via the HTTP Referer header. NOTE: This vulnerability only affects products that are no longer supported by the maintainer. NOTE: this is typically not exploitable because of URL encoding (except in Internet Explorer) and because a web page cannot specify that a client should make an additional HTTP request with an arbitrary Referer header.
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Analysis
by VulDB Data Team • 05/05/2025
The vulnerability identified as CVE-2020-25786 represents a cross-site scripting flaw discovered in D-Link DIR-816L and DIR-803 router models running specific firmware versions. This security weakness exists within the web interface component located at webinc/js/info.php, which processes HTTP Referer headers without adequate input sanitization. The affected devices operate under firmware versions 2.06.B09_BETA for DIR-816L and 1.04.B02 for DIR-803, both of which are no longer supported by the vendor, making this vulnerability particularly concerning from a security maintenance perspective.
The technical exploitation of this vulnerability occurs through manipulation of the HTTP Referer header, which is automatically included by web browsers when making requests to web servers. When a malicious user crafts a specially formatted Referer header containing script code, the vulnerable web interface fails to properly escape or validate this input before rendering it in the browser context. This creates an opportunity for attackers to inject malicious JavaScript code that executes in the context of authenticated users visiting the affected router's web interface. The vulnerability is categorized under CWE-79, which specifically addresses cross-site scripting flaws in web applications, and aligns with ATT&CK technique T1212 for exploitation of web application vulnerabilities.
The operational impact of this vulnerability extends beyond simple script injection, as it could potentially enable attackers to perform session hijacking, steal administrative credentials, or manipulate router configurations through authenticated user sessions. However, the exploitability of this vulnerability is significantly limited by modern browser security mechanisms, particularly URL encoding that prevents many XSS payloads from executing. The vulnerability's practical exploitability is further constrained by the fact that web pages cannot directly control or force browsers to send arbitrary Referer headers, making this attack vector particularly challenging to leverage in real-world scenarios. Despite these mitigating factors, the vulnerability remains a concern for organizations still operating unsupported devices, as these routers may lack modern security features and regular patching cycles.
The remediation approach for this vulnerability is fundamentally limited by the end-of-life status of the affected firmware versions, as D-Link has ceased support for these products. Organizations should consider immediate hardware replacement with supported router models that receive regular security updates and patches. Network segmentation strategies can provide additional protection by limiting access to these vulnerable devices to authorized personnel only, while implementing web application firewalls may offer some protection against certain types of XSS attacks. Security teams should also conduct comprehensive inventory audits to identify all instances of these unsupported devices within their network infrastructure, as they represent significant attack surface vulnerabilities that could be exploited in targeted attacks against network infrastructure. The vulnerability demonstrates the critical importance of maintaining supported firmware versions and the risks associated with operating legacy network equipment that no longer receives security updates from vendors.