CVE-2025-45835 is a high-severity null pointer dereference vulnerability identified in the Netis WF2880 router, specifically in version 2.1.40207. The flaw resides within the FUN_004904c8 function of the cgitest.cgi file, which is part of the device's web interface. An attacker can exploit this vulnerability by manipulating the CONTENT_LENGTH environment variable, which is used to indicate the size of the HTTP request body. By controlling this value, the attacker can cause the program to dereference a null pointer, leading to a crash of the affected process. This crash results in a denial-of-service (DoS) condition, rendering the device or its web management interface temporarily unavailable. The vulnerability requires no authentication or user interaction and can be exploited remotely over the network, as indicated by the CVSS vector (AV:N/AC:L/PR:N/UI:N). Although the vulnerability does not directly compromise confidentiality or integrity, the availability impact is significant. There are currently no known exploits in the wild, and no patches have been linked yet. The vulnerability is classified under CWE-476 (NULL Pointer Dereference), a common software flaw that can cause instability and service disruption. Given the nature of the device—a consumer and small business router—this vulnerability could be leveraged by attackers to disrupt network connectivity or management capabilities, potentially as part of a larger attack campaign or to facilitate further exploitation by causing denial of service and forcing device reboots or resets.

For European organizations, the impact of this vulnerability can be substantial, particularly for small and medium enterprises (SMEs) and home office environments that rely on Netis WF2880 routers for internet connectivity and network management. A successful DoS attack could interrupt business operations by disabling internet access or remote management capabilities, leading to productivity losses and potential operational downtime. In critical environments such as healthcare, education, or public services where continuous connectivity is essential, such disruptions could have cascading effects. Additionally, attackers might use this vulnerability as a stepping stone to conduct more sophisticated attacks by causing device instability or forcing users to reset devices to default configurations, potentially exposing them to further compromise. Although the vulnerability does not allow direct data theft or code execution, the loss of availability can degrade trust in network infrastructure and complicate incident response efforts. Given the remote exploitability without authentication, attackers can target vulnerable devices en masse, increasing the risk of widespread disruption across European networks that deploy this router model.

To mitigate CVE-2025-45835, European organizations should first inventory their network devices to identify any Netis WF2880 routers running version 2.1.40207. Immediate mitigation steps include restricting access to the router's web management interface by implementing network segmentation and firewall rules to limit access to trusted IP addresses only. Disabling remote management features, if not required, can reduce exposure. Network administrators should monitor router logs and network traffic for unusual requests that manipulate HTTP headers, particularly CONTENT_LENGTH values. Since no official patches are currently available, organizations should engage with Netis support channels to obtain firmware updates or advisories. Where possible, upgrading to newer firmware versions that address this vulnerability is recommended once released. As a temporary workaround, deploying network-based intrusion prevention systems (IPS) or web application firewalls (WAF) to detect and block malformed HTTP requests targeting cgitest.cgi can help prevent exploitation attempts. Additionally, educating users and administrators about the risks of exposing router management interfaces to the internet and enforcing strong access controls will reduce attack surface.