CVE-2025-5912 is a critical security vulnerability identified in the D-Link DIR-632 router, specifically affecting firmware version FW103B08. The flaw resides in the HTTP POST Request Handler component, within the function do_file, where improper handling of input data leads to a stack-based buffer overflow. This type of vulnerability allows an attacker to overwrite the stack memory, potentially enabling arbitrary code execution, denial of service, or system compromise. The vulnerability can be exploited remotely without any user interaction or prior authentication, making it highly dangerous. The CVSS 4.0 base score is 8.7, reflecting high severity due to the ease of remote exploitation (network attack vector), no required privileges, and no user interaction. The vulnerability affects only devices running an outdated and no longer supported firmware version, and no official patches or mitigations have been released by D-Link. Although no exploits have been reported in the wild yet, the public disclosure of the exploit code increases the risk of active exploitation by threat actors.

For European organizations, the impact of this vulnerability can be significant, especially for those still using the affected D-Link DIR-632 devices with the vulnerable firmware. Successful exploitation could lead to full compromise of the router, allowing attackers to intercept, manipulate, or disrupt network traffic, potentially leading to data breaches, lateral movement within corporate networks, or denial of service conditions. This is particularly concerning for small and medium enterprises or home office setups that rely on this router model for internet connectivity and may lack robust network segmentation or monitoring. The lack of vendor support and patches means organizations must rely on alternative mitigation strategies. Given the critical nature of the flaw and the possibility of remote exploitation without authentication, the threat could be leveraged by cybercriminals or state-sponsored actors targeting European networks for espionage or disruption.

Since no official patches are available for the affected firmware, organizations should prioritize replacing the D-Link DIR-632 routers running FW103B08 with newer, supported devices that receive regular security updates. If immediate replacement is not feasible, network administrators should implement strict network segmentation to isolate vulnerable devices from critical infrastructure and sensitive data. Deploying firewall rules to restrict inbound HTTP POST requests to the router's management interface from untrusted networks can reduce exposure. Monitoring network traffic for unusual patterns or signs of exploitation attempts is also recommended. Additionally, disabling remote management features on the router and changing default credentials can help reduce attack surface. Organizations should maintain an inventory of network devices to identify any remaining vulnerable units and plan for their timely decommissioning.