CVE-2025-4140 is a critical buffer overflow vulnerability identified in the Netgear EX6120 wireless range extender, specifically version 1.0.3.94. The flaw resides in the function sub_30394, where improper handling of the 'host' argument allows an attacker to overflow a buffer. This vulnerability can be exploited remotely without requiring user interaction or prior authentication, making it highly accessible to attackers. The buffer overflow can lead to arbitrary code execution, potentially allowing an attacker to take full control of the affected device. Given the nature of the device—a network extender that bridges wireless and wired networks—compromise could enable attackers to intercept, manipulate, or disrupt network traffic. The vulnerability has a CVSS 4.0 base score of 8.7 (high severity), with attack vector network (AV:N), low attack complexity (AC:L), no privileges required (PR:L), no user interaction (UI:N), and high impact on confidentiality, integrity, and availability (VC:H, VI:H, VA:H). The vendor has not responded to disclosure attempts, and no patches or mitigations have been published yet. No known exploits are currently reported in the wild, but the ease of exploitation and critical impact make this a significant threat to networks utilizing this device.

European organizations using the Netgear EX6120 in their network infrastructure face substantial risks. Successful exploitation could lead to full device compromise, enabling attackers to intercept sensitive communications, inject malicious traffic, or disrupt network availability. This is particularly concerning for small and medium enterprises (SMEs) and home office environments that rely on consumer-grade network extenders without advanced security monitoring. Compromise of these devices could serve as a foothold for lateral movement into corporate networks, especially if the extender connects to internal resources. Critical sectors such as finance, healthcare, and government agencies using these devices may experience data breaches, operational disruptions, and potential regulatory non-compliance under GDPR due to unauthorized data exposure. The lack of vendor response and absence of patches increases the window of exposure, elevating the risk of exploitation over time.

1. Immediate network segmentation: Isolate Netgear EX6120 devices from critical internal networks to limit potential lateral movement if compromised. 2. Disable remote management features on the EX6120 to reduce attack surface. 3. Monitor network traffic for unusual patterns originating from or directed to the extender, using IDS/IPS solutions tuned to detect buffer overflow exploit attempts. 4. Replace affected devices with alternative models or vendors that have confirmed patches or no known vulnerabilities. 5. If replacement is not immediately feasible, implement strict firewall rules to restrict inbound and outbound traffic to/from the extender. 6. Conduct regular vulnerability scans and penetration tests focusing on network extenders and IoT devices. 7. Maintain up-to-date asset inventories to quickly identify and remediate vulnerable devices. 8. Engage with Netgear support channels persistently for updates or patches, and consider reporting to national cybersecurity authorities to raise awareness.