CVE-2025-5630 is a critical security vulnerability identified in the D-Link DIR-816 router, specifically version 1.10CNB05. The vulnerability is a stack-based buffer overflow occurring in the handling of the 'ip' argument within the /goform/form2lansetup.cgi endpoint. This endpoint is part of the router's web interface used for LAN setup configuration. The flaw allows an unauthenticated remote attacker to send specially crafted requests to this CGI script, causing a buffer overflow on the stack. This can lead to arbitrary code execution with the privileges of the web server process, potentially allowing full control over the device. The vulnerability is classified as critical with a CVSS 4.0 base score of 9.3, reflecting its high impact and ease of exploitation (network vector, no authentication or user interaction required). The affected product is no longer supported by the vendor, meaning no official patches or updates are available, increasing the risk for users who continue to operate this device. Although no known exploits have been reported in the wild yet, the public disclosure of the exploit code raises the likelihood of imminent attacks. The vulnerability impacts the confidentiality, integrity, and availability of the device and any network it protects, as attackers could use compromised routers to intercept traffic, launch further attacks, or disrupt network operations.

For European organizations, this vulnerability poses a significant risk, especially for small and medium enterprises or home offices that may still use the D-Link DIR-816 router due to its affordability and availability. Compromise of these routers could lead to unauthorized access to internal networks, interception of sensitive data, and disruption of business operations. Since the device is often deployed at network perimeters, attackers gaining control could pivot to internal systems or use the router as a foothold for broader attacks. The lack of vendor support means organizations cannot rely on official patches, increasing exposure. Additionally, the critical severity and remote exploitability without authentication make it a prime target for automated scanning and exploitation campaigns. This could lead to widespread compromise, data breaches, and potential regulatory non-compliance under GDPR if personal data is exposed. The impact is heightened in sectors with strict security requirements such as finance, healthcare, and government entities that might still use legacy network equipment.

Given the absence of vendor patches, European organizations should prioritize immediate mitigation steps beyond generic advice: 1) Replace the affected D-Link DIR-816 devices with modern, supported routers that receive regular security updates. 2) If replacement is not immediately feasible, isolate these routers on segmented network zones with strict firewall rules to limit exposure to untrusted networks, especially the internet. 3) Disable remote management interfaces and restrict access to the router’s web interface to trusted internal IP addresses only. 4) Monitor network traffic for unusual activity indicative of exploitation attempts targeting the /goform/form2lansetup.cgi endpoint. 5) Employ network intrusion detection/prevention systems (IDS/IPS) with signatures tuned to detect exploitation attempts of this specific vulnerability. 6) Educate IT staff and users about the risks of legacy devices and the importance of timely hardware upgrades. 7) Maintain up-to-date network asset inventories to identify and track vulnerable devices. These targeted actions will reduce the attack surface and limit potential damage until full device replacement is achieved.