CVE-2025-5969 is a critical stack-based buffer overflow vulnerability identified in the D-Link DIR-632 router, specifically affecting firmware version FW103B08. The vulnerability resides in the HTTP POST request handler component, within the function FUN_00425fd8 of the /biurl_grou file. An attacker can remotely exploit this flaw by sending specially crafted HTTP POST requests to the affected device, causing a stack-based buffer overflow. This type of vulnerability can lead to arbitrary code execution, potentially allowing an attacker to take full control of the device. The vulnerability does not require user interaction or authentication, making it highly exploitable over the network. Although the affected product is no longer supported by the vendor, the exploit details have been publicly disclosed, increasing the risk of exploitation by threat actors. The CVSS v4.0 score is 8.7 (high severity), reflecting the vulnerability's network attack vector, low attack complexity, no privileges required, and no user interaction needed, combined with high impacts on confidentiality, integrity, and availability. No patches are currently available from the vendor, and no known exploits in the wild have been reported yet, but the public disclosure raises the likelihood of imminent exploitation attempts.

For European organizations, the exploitation of CVE-2025-5969 could have severe consequences. The D-Link DIR-632 router is commonly used in small to medium-sized business environments and home offices, which means that compromised devices could serve as entry points into corporate or residential networks. Successful exploitation could lead to unauthorized access, data exfiltration, network disruption, or pivoting attacks within the internal network. Given the router's role in managing network traffic, attackers could intercept or manipulate sensitive communications, impacting confidentiality and integrity. The lack of vendor support and patches increases the risk, as organizations cannot rely on official updates to remediate the vulnerability. This situation is particularly critical for sectors with stringent data protection requirements under GDPR, such as finance, healthcare, and critical infrastructure. Additionally, compromised routers could be leveraged in botnets or distributed denial-of-service (DDoS) attacks, further amplifying the threat to European network stability and security.

Since the affected D-Link DIR-632 devices are no longer supported and no official patches are available, organizations should prioritize the following mitigations: 1) Immediate network segmentation to isolate vulnerable routers from critical systems and sensitive data; 2) Replace or upgrade affected devices with currently supported hardware that receives regular security updates; 3) Implement strict firewall rules to restrict inbound HTTP POST requests to the router's management interface, ideally limiting access to trusted IP addresses only; 4) Monitor network traffic for unusual POST requests or signs of exploitation attempts targeting the router; 5) Employ intrusion detection/prevention systems (IDS/IPS) with signatures or heuristics capable of detecting buffer overflow attempts against HTTP services; 6) Educate users and administrators about the risks of using unsupported network hardware; 7) Regularly audit network devices to identify and inventory unsupported or end-of-life equipment; 8) If replacement is not immediately feasible, consider disabling remote management features and restricting local management access to trusted personnel only.