CVE-2025-7836 in DIR-816L
Summary
by MITRE • 07/19/2025
A vulnerability has been found in D-Link DIR-816L up to 2.06B01 and classified as critical. Affected by this vulnerability is the function lxmldbc_system of the file /htdocs/cgibin of the component Environment Variable Handler. The manipulation leads to command injection. The attack can be launched remotely. The exploit has been disclosed to the public and may be used. This vulnerability only affects products that are no longer supported by the maintainer.
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Analysis
by VulDB Data Team • 10/03/2025
The CVE-2025-7836 vulnerability represents a critical command injection flaw in D-Link DIR-816L routers running firmware versions up to 2.06B01. This vulnerability resides within the lxmldbc_system function of the environment variable handler component, specifically located in the /htdocs/cgibin directory of the device's web interface. The flaw allows attackers to execute arbitrary commands on the affected device through remote exploitation, making it particularly dangerous for network-connected systems. The vulnerability's classification as critical stems from its potential to enable complete system compromise, including unauthorized access to network resources and possible lateral movement within compromised networks. The fact that this vulnerability has been publicly disclosed and is actively exploitable significantly increases the risk to affected devices, as malicious actors can leverage existing exploits without requiring advanced technical skills.
The technical implementation of this vulnerability involves improper input validation within the environment variable handler component, specifically in how the lxmldbc_system function processes user-supplied data. When the web interface receives requests containing maliciously crafted parameters through the Environment Variable Handler component, the system fails to properly sanitize or escape these inputs before incorporating them into system commands. This lack of proper input validation creates an injection point where attacker-controlled commands can be executed with the privileges of the web server process, which typically runs with elevated permissions on the router. The vulnerability's location in the /htdocs/cgibin directory indicates it operates within the web application's CGI execution environment, making it accessible through standard HTTP requests to the router's web interface.
The operational impact of CVE-2025-7836 extends far beyond simple unauthorized access, as it provides attackers with complete control over affected D-Link DIR-816L devices. Once exploited, attackers can modify router configurations, establish persistent backdoors, monitor network traffic, and potentially use the compromised device as a launch point for attacks against other systems within the local network. The vulnerability's remote exploitation capability means that attackers do not need physical access to the device, significantly expanding the attack surface and making it particularly dangerous for home and small office networks. Given that these routers are no longer supported by the vendor, users cannot receive official security patches, leaving them vulnerable to exploitation for an indefinite period. This situation creates a significant risk for organizations and individuals who have not yet upgraded their router firmware or replaced the affected hardware.
The vulnerability aligns with CWE-77 and CWE-94 categories, specifically representing a command injection vulnerability that allows arbitrary code execution through improper input validation. From an ATT&CK framework perspective, this vulnerability maps to techniques such as T1059.001 (Command and Scripting Interpreter: PowerShell) and T1068 (Exploitation for Privilege Escalation) where the initial compromise leads to full system control. Organizations should implement immediate mitigations including network segmentation to isolate affected devices, disabling unnecessary web services, and implementing network monitoring to detect suspicious traffic patterns. The most effective long-term solution involves replacing all affected D-Link DIR-816L devices with supported models, as the lack of vendor support means no future security updates will be available. Additionally, users should conduct thorough network audits to identify other potentially vulnerable devices and implement robust network access controls to minimize the impact of any successful exploitation attempts.