CVE-2025-15391 is a medium-severity command injection vulnerability found in the D-Link DIR-806A router, specifically in the SSDP Request Handler component's ssdpcgi_main function. The vulnerability arises due to improper input validation or sanitization in the SSDP CGI interface, allowing remote attackers to inject and execute arbitrary system commands on the device. The attack vector is network-based and requires no authentication or user interaction, making it remotely exploitable over the internet or local network. The affected firmware version is 100CNb11, and the product is no longer supported by D-Link, meaning no official security patches or firmware updates are available to remediate the issue. The CVSS 4.0 vector indicates low complexity and no privileges required, but the impact on confidentiality, integrity, and availability is limited to low or partial, resulting in a medium overall severity score of 5.3. Although no known exploits are currently observed in the wild, public exploit code has been released, increasing the risk of future attacks. Successful exploitation could allow attackers to execute arbitrary commands, potentially gaining control over the router, intercepting or manipulating network traffic, or causing denial of service. The vulnerability affects the router's core network functionality, making it a significant risk for environments relying on this device for internet connectivity or internal network routing. Since the device is unsupported, organizations must consider alternative mitigation strategies such as device replacement or network isolation.

For European organizations, the impact of CVE-2025-15391 can be significant if the affected D-Link DIR-806A routers are deployed in critical network segments. Exploitation could lead to unauthorized command execution, enabling attackers to manipulate network traffic, intercept sensitive data, disrupt internet connectivity, or pivot to other internal systems. This could compromise confidentiality, integrity, and availability of organizational networks. The lack of vendor support and patches increases the risk, as vulnerable devices remain exposed. Small and medium enterprises or home office environments using this router model are particularly vulnerable due to limited IT security resources. Critical infrastructure sectors such as energy, healthcare, and finance in Europe could face operational disruptions if these routers are part of their network infrastructure. Additionally, the public availability of exploit code raises the likelihood of opportunistic attacks, including from cybercriminals or hacktivists targeting European networks. The medium severity rating reflects a moderate but tangible risk that requires proactive mitigation to prevent potential breaches or service outages.

Given the absence of official patches for the unsupported D-Link DIR-806A 100CNb11 firmware, the primary mitigation is to replace the affected devices with currently supported and securely maintained hardware. Organizations should conduct an inventory to identify any deployments of this router model and prioritize their removal. If immediate replacement is not feasible, network segmentation should be implemented to isolate vulnerable routers from critical systems and sensitive data. Disabling SSDP services or restricting access to the SSDP CGI interface via firewall rules can reduce exposure to remote exploitation. Monitoring network traffic for anomalous SSDP requests or unusual command execution patterns can help detect exploitation attempts early. Employing intrusion detection/prevention systems (IDS/IPS) with signatures for this vulnerability may provide additional defense. Regularly updating network device inventories and enforcing strict network access controls will limit the attack surface. Finally, educating users and administrators about the risks of using unsupported network devices is essential to prevent future exposure.