CVE-2025-50635 is a high-severity null pointer dereference vulnerability identified in the Netis WF2780 router firmware version 2.2.35445. The flaw resides in the FUN_0048a728 function within the cgitest.cgi file, a CGI script component of the device's web management interface. Specifically, the vulnerability can be triggered by an attacker manipulating the CONTENT_LENGTH HTTP header value, which is used by the CGI script to determine the size of incoming data. By controlling this variable, an attacker can cause the function to dereference a null pointer, leading to a crash of the program. This crash results in a denial-of-service (DoS) condition, rendering the device unresponsive or requiring a reboot. The vulnerability does not allow for code execution or data leakage but impacts availability. The CVSS v3.1 base score is 7.5, reflecting a network attack vector (AV:N), low attack complexity (AC:L), no privileges required (PR:N), no user interaction (UI:N), unchanged scope (S:U), no confidentiality or integrity impact (C:N/I:N), and high availability impact (A:H). No known exploits have been reported in the wild yet, and no patches have been linked at this time. The vulnerability is categorized under CWE-476 (NULL Pointer Dereference), a common programming error that can cause crashes and instability.

For European organizations, the primary impact of CVE-2025-50635 is the potential disruption of network connectivity and management due to denial-of-service conditions on affected Netis WF2780 routers. This can interrupt business operations, especially for small and medium enterprises (SMEs) or branch offices relying on these consumer-grade or SOHO routers for internet access and internal network routing. The DoS could be exploited remotely without authentication, increasing the risk of widespread disruption. While the vulnerability does not compromise data confidentiality or integrity, the loss of availability can affect critical services, remote work capabilities, and network monitoring. In sectors such as healthcare, finance, or critical infrastructure where continuous network uptime is essential, even short outages can have significant operational and regulatory consequences. Additionally, the lack of patches means organizations must rely on mitigation strategies until a firmware update is released. The vulnerability's exploitation requires only network access, which could be from the internet or internal network, depending on router configuration, increasing the attack surface.

European organizations using Netis WF2780 routers should immediately assess their exposure to this vulnerability. Specific mitigation steps include: 1) Restricting access to the router's web management interface by disabling remote management over the internet or limiting it to trusted IP addresses via firewall rules. 2) Implementing network segmentation to isolate vulnerable devices from critical network segments and sensitive data. 3) Monitoring network traffic for unusual HTTP requests that manipulate CONTENT_LENGTH headers or target cgitest.cgi endpoints. 4) Temporarily disabling or restricting CGI scripts if possible, or disabling the vulnerable web interface if it is not essential. 5) Keeping an eye on vendor announcements for firmware updates or patches addressing this vulnerability and applying them promptly once available. 6) Employing intrusion detection/prevention systems (IDS/IPS) with custom signatures to detect attempts to exploit this null pointer dereference. 7) Conducting regular backups and having incident response plans to quickly recover from potential DoS incidents. These targeted measures go beyond generic advice by focusing on access control, monitoring, and isolation specific to the vulnerability's exploitation vector.