CVE-2025-13189 is a stack-based buffer overflow vulnerability identified in the D-Link DIR-816L router, specifically affecting the genacgi_main function within the gena.cgi CGI script. The vulnerability arises from improper handling of the SERVER_ID or HTTP_SID parameters, which an attacker can manipulate remotely to overflow the stack buffer. This overflow can corrupt memory, potentially allowing arbitrary code execution or causing a denial of service by crashing the device. The attack vector is network-based (AV:N), requires no user interaction (UI:N), and no authentication (AT:N), making it easily exploitable remotely. The affected firmware version is 2_06_b09_beta, which is no longer supported by D-Link, meaning no official patches or updates are available. The CVSS 4.0 score of 8.7 reflects the high impact on confidentiality, integrity, and availability, with low attack complexity and no privileges required. While no exploits have been observed in the wild yet, the public disclosure of the vulnerability increases the risk of exploitation. The vulnerability is particularly concerning for environments where these routers are used as edge devices or in critical network segments, as compromise could lead to network infiltration or disruption.

For European organizations, the impact of CVE-2025-13189 can be significant, especially for those still operating the affected D-Link DIR-816L routers with the vulnerable firmware. Successful exploitation could allow attackers to execute arbitrary code remotely, leading to full device compromise. This could result in interception or manipulation of network traffic, unauthorized access to internal networks, or disruption of services. Given that the device is often used in small office/home office (SOHO) environments, compromised routers could serve as entry points for broader attacks against organizational networks. The lack of vendor support means no official patches are available, increasing the risk of prolonged exposure. Critical infrastructure or organizations with less mature network security practices may face heightened risks. Additionally, the vulnerability could be leveraged in botnet campaigns or ransomware attacks targeting vulnerable routers, amplifying the threat landscape in Europe.

Since the affected firmware version 2_06_b09_beta is no longer supported and no official patches exist, European organizations should prioritize the following mitigations: 1) Immediate replacement of the D-Link DIR-816L devices with supported and updated hardware models to eliminate the vulnerability. 2) If replacement is not immediately feasible, isolate the vulnerable routers from the internet and sensitive internal networks by implementing strict network segmentation and firewall rules restricting access to the router’s management interfaces. 3) Disable remote management features and any unnecessary services on the device to reduce the attack surface. 4) Monitor network traffic for unusual activity indicative of exploitation attempts, such as unexpected CGI requests targeting SERVER_ID or HTTP_SID parameters. 5) Employ intrusion detection/prevention systems (IDS/IPS) with signatures or heuristics capable of detecting exploitation attempts against this vulnerability. 6) Educate IT staff about the risks of using unsupported firmware and the importance of timely device updates or replacements. 7) Maintain an inventory of network devices to identify and track vulnerable routers for prioritized remediation.