CVE-2026-1544 is an OS command injection vulnerability identified in the D-Link DIR-823X router firmware version 250416. The vulnerability resides in the function sub_41E2A0 within the /goform/set_mode endpoint, where the lan_gateway parameter is improperly sanitized. This flaw allows an attacker to inject arbitrary operating system commands remotely without requiring user interaction or authentication, though low privileges are needed. The vulnerability arises from insufficient input validation, enabling crafted HTTP requests to execute commands on the underlying operating system. The exploit can be triggered by sending manipulated parameters to the router’s web interface, potentially allowing attackers to gain control over the device, manipulate network traffic, or pivot to internal networks. The affected product is no longer supported by D-Link, meaning no official patches or firmware updates are available, increasing the risk of exploitation. The CVSS 4.0 score is 5.3 (medium), reflecting the ease of remote exploitation but limited scope and impact due to required privileges and lack of user interaction. While no active exploitation has been reported, a public exploit is available, raising the threat level. This vulnerability highlights the risks associated with legacy network devices that remain in operation without vendor support.

For European organizations, this vulnerability poses a significant risk to network infrastructure security. Compromise of the DIR-823X routers could lead to unauthorized access to internal networks, interception or manipulation of network traffic, and potential lateral movement to other critical systems. The lack of vendor support means that organizations cannot rely on official patches, increasing exposure time. This is particularly concerning for small and medium enterprises or home office environments where such consumer-grade routers are common. Disruption of router availability could also impact business continuity. Confidentiality and integrity of data traversing the network may be compromised, leading to data breaches or espionage. The medium severity score reflects moderate impact, but the ease of remote exploitation without user interaction elevates the threat. European entities with legacy network devices should consider this vulnerability a priority for risk management.

Given the absence of official patches, European organizations should implement compensating controls. Immediate mitigation includes isolating affected routers from critical network segments and restricting access to the router’s management interface via firewall rules or network segmentation. Replacing the DIR-823X devices with supported, updated hardware is strongly recommended to eliminate the vulnerability. If replacement is not immediately feasible, disabling remote management features and restricting local management access to trusted administrators can reduce attack surface. Network monitoring for unusual traffic patterns or command injection attempts targeting /goform/set_mode should be implemented. Employing intrusion detection/prevention systems (IDS/IPS) with signatures for this exploit can help detect and block attacks. Regularly auditing network devices for unsupported firmware and maintaining an asset inventory will aid in proactive vulnerability management. Educating users about the risks of legacy devices and enforcing strict network access controls are also important.