CVE-2025-5620 is a security vulnerability identified in the D-Link DIR-816 router, specifically version 1.10CNB05. The flaw exists in the setipsec_config function within the /goform/setipsec_config endpoint. This vulnerability arises from improper sanitization of the localIP and remoteIP parameters, which allows an attacker to inject arbitrary OS commands. Because the vulnerable function processes these parameters without adequate validation, an attacker can remotely execute commands on the underlying operating system with the privileges of the affected service. The vulnerability is remotely exploitable without requiring authentication or user interaction, increasing its risk profile. Although the CVSS v4.0 score is 6.9, categorized as medium severity, the potential for remote command execution typically elevates concern. However, it is important to note that this vulnerability affects only the D-Link DIR-816 model running firmware version 1.10CNB05, which is no longer supported by the vendor. No official patches or updates have been released to address this issue, and no known exploits have been observed in the wild at the time of publication. The public disclosure of the exploit code increases the likelihood of exploitation attempts, especially against unpatched devices still in operation. The vulnerability impacts the confidentiality, integrity, and availability of affected devices, as attackers could execute arbitrary commands, potentially leading to device compromise, network pivoting, or denial of service.

For European organizations, the impact of CVE-2025-5620 depends largely on the presence and deployment of the affected D-Link DIR-816 routers. If these devices are used within corporate or critical infrastructure networks, the vulnerability could allow attackers to gain unauthorized control over network gateways, leading to data breaches, interception of network traffic, or disruption of network services. The ability to execute OS commands remotely without authentication means attackers could install malware, create persistent backdoors, or disrupt network operations. Given that the product is no longer supported, organizations relying on these devices face increased risk due to the absence of vendor patches. This could be particularly problematic for small and medium enterprises or home office environments where such routers might still be in use. The public availability of exploit code further raises the risk of opportunistic attacks targeting vulnerable devices in Europe, potentially affecting confidentiality and availability of organizational networks.

Since no official patches are available due to the product being out of support, European organizations should prioritize the following mitigations: 1) Immediate identification and inventory of all D-Link DIR-816 routers running version 1.10CNB05 within their networks. 2) Replacement of affected devices with supported and updated hardware models to eliminate the vulnerability. 3) If replacement is not immediately feasible, isolate the vulnerable routers from critical network segments and restrict remote management interfaces to trusted IP addresses only. 4) Disable remote administration features on the affected devices to reduce exposure. 5) Implement network-level intrusion detection and prevention systems to monitor for suspicious activities targeting the /goform/setipsec_config endpoint or unusual command execution patterns. 6) Employ network segmentation to limit the impact of a compromised router. 7) Educate IT staff about the risks associated with unsupported hardware and the importance of timely hardware lifecycle management. 8) Regularly monitor threat intelligence feeds for any emerging exploits related to this vulnerability to respond promptly.