CVE-2025-13189 is a stack-based buffer overflow vulnerability identified in the D-Link DIR-816L router, specifically in firmware version 2_06_b09_beta. The vulnerability exists in the genacgi_main function within the gena.cgi file, where improper validation of the SERVER_ID/HTTP_SID parameters allows an attacker to overflow the stack. This overflow can be triggered remotely without requiring authentication or user interaction, enabling remote code execution on the affected device. The vulnerability has a CVSS 4.0 base score of 8.7, indicating high severity, with network attack vector, low attack complexity, no privileges required, and no user interaction needed. The impact on confidentiality, integrity, and availability is high, as successful exploitation can lead to full device compromise, allowing attackers to manipulate network traffic, intercept data, or disrupt services. Although the product is no longer supported by D-Link and no official patches are available, proof-of-concept exploit code has been publicly disclosed, increasing the likelihood of exploitation by threat actors. The vulnerability affects only the specified beta firmware version, but devices running this or similar outdated firmware remain vulnerable. Due to the lack of vendor support, mitigation relies heavily on network-level controls and device replacement. This vulnerability highlights risks associated with legacy network equipment in operational environments.

For European organizations, the exploitation of CVE-2025-13189 could result in complete compromise of affected D-Link DIR-816L routers, leading to unauthorized access to internal networks, interception or manipulation of sensitive data, and potential disruption of network services. This is particularly critical for small and medium enterprises (SMEs) and home office environments where such consumer-grade routers are commonly deployed and may lack robust security monitoring. The vulnerability’s remote exploitability without authentication increases the risk of widespread attacks, especially if attackers scan for vulnerable devices exposed to the internet. Compromised routers can serve as footholds for lateral movement or as launch points for further attacks within corporate networks. The lack of vendor support means no official patches are available, prolonging exposure and complicating remediation efforts. Additionally, the public availability of exploit code lowers the barrier for attackers, increasing the threat landscape. The impact extends beyond confidentiality and integrity to availability, as attackers could disrupt network connectivity or launch denial-of-service conditions. Overall, this vulnerability poses a significant operational and security risk to European organizations relying on this hardware or firmware version.

Given the absence of official patches for the affected firmware, European organizations should prioritize immediate replacement of D-Link DIR-816L devices running version 2_06_b09_beta with supported and updated hardware. Where replacement is not immediately feasible, network segmentation should be implemented to isolate vulnerable routers from critical internal systems and sensitive data. Access to router management interfaces must be restricted using firewall rules to allow only trusted IP addresses and disable remote management features if enabled. Intrusion detection and prevention systems should be configured to monitor and block suspicious traffic targeting the vulnerable CGI endpoint. Regular network scans should be conducted to identify devices running the vulnerable firmware. Organizations should also enforce strict network access controls and consider deploying network-level anomaly detection to identify exploitation attempts. Employee awareness programs should highlight risks associated with legacy network devices. Finally, organizations should maintain an inventory of all network devices to ensure timely identification and decommissioning of unsupported hardware.