CVE-2025-6121 is a critical stack-based buffer overflow vulnerability found in the D-Link DIR-632 router, specifically in firmware version FW103B08. The flaw resides in the HTTP POST Request Handler component, within the function get_pure_content. An attacker can exploit this vulnerability by manipulating the Content-Length HTTP header in a POST request, causing a stack-based buffer overflow. This overflow can lead to arbitrary code execution on the device without requiring any authentication or user interaction, and the attack can be launched remotely over the network. Although the affected product is no longer supported by D-Link, the vulnerability remains exploitable. The CVSS v4.0 score of 9.3 reflects the high impact on confidentiality, integrity, and availability, combined with the ease of exploitation (network vector, no privileges or user interaction required). No official patches are available due to the product's end-of-life status, and while no known exploits have been observed in the wild yet, public disclosure of the exploit code increases the risk of imminent attacks. The vulnerability affects only the specific firmware version FW103B08 of the DIR-632 model, which is a consumer-grade wireless router commonly used in small offices and home environments. The stack-based buffer overflow could allow attackers to execute arbitrary code, potentially taking full control of the device, intercepting or modifying network traffic, or launching further attacks on internal networks.

For European organizations, the exploitation of CVE-2025-6121 could have significant consequences, especially for small and medium-sized enterprises (SMEs) and home office setups relying on the D-Link DIR-632 router. Compromise of these routers could lead to unauthorized access to internal networks, interception of sensitive communications, and lateral movement to other critical systems. Given the router’s role as a network gateway, attackers could disrupt availability by causing device crashes or persistent denial-of-service conditions. The lack of vendor support means no official patches are available, increasing the risk of prolonged exposure. Additionally, the public availability of exploit code lowers the barrier for attackers, including cybercriminals and potentially state-sponsored actors, to weaponize this vulnerability. This could lead to targeted attacks on European organizations with weak network perimeter defenses, especially those that have not replaced or upgraded legacy network equipment. The vulnerability also poses risks to privacy and data protection compliance under regulations like GDPR if personal data is intercepted or manipulated. Overall, the impact is critical for affected environments, with potential cascading effects on business continuity and data security.

Given the absence of official patches, European organizations should prioritize the following practical mitigation steps: 1) Immediate identification and inventory of all D-Link DIR-632 devices running firmware FW103B08 within their networks. 2) Where possible, replace affected routers with newer, supported models that receive regular security updates. 3) If replacement is not immediately feasible, isolate the vulnerable devices by segmenting them into dedicated network zones with strict access controls to limit exposure. 4) Disable remote management interfaces and restrict administrative access to trusted internal IP addresses only. 5) Implement network-level protections such as intrusion detection/prevention systems (IDS/IPS) configured to detect anomalous HTTP POST requests with suspicious Content-Length headers. 6) Monitor network traffic for unusual patterns indicative of exploitation attempts, including unexpected crashes or reboots of the router. 7) Educate users and IT staff about the risks associated with legacy network devices and the importance of timely hardware lifecycle management. 8) Consider deploying compensating controls like VPNs or encrypted tunnels to protect sensitive communications passing through vulnerable routers. These steps go beyond generic advice by focusing on device-specific actions and network architecture adjustments to mitigate risk in the absence of vendor patches.