CVE-2025-8818 is a medium-severity OS command injection vulnerability affecting multiple Linksys range extender models, including RE6250, RE6300, RE6350, RE6500, RE7000, and RE9000, with firmware versions up to 20250801. The vulnerability resides in the setDFSSetting function within the /goform/setLan endpoint, where improper sanitization of the lanNetmask and lanIp parameters allows an attacker to inject arbitrary operating system commands. This flaw can be exploited remotely without requiring user interaction or authentication, as indicated by the CVSS vector (AV:N/AC:L/AT:N/UI:N/PR:L). The vulnerability impacts confidentiality, integrity, and availability due to the potential for arbitrary command execution on the device, which could lead to device compromise, network pivoting, or denial of service. Although the vendor was notified early, no patch or response has been issued, and no known exploits are currently observed in the wild. The disclosure is public, increasing the risk of exploitation by threat actors. The vulnerability's medium CVSS score (5.3) reflects the requirement for low privileges (PR:L) but no user interaction or complex attack conditions. The affected devices are commonly used in home and small office environments to extend wireless network coverage, making them potential entry points for attackers targeting internal networks.

For European organizations, especially small and medium enterprises (SMEs) and home office users relying on Linksys range extenders, this vulnerability poses a significant risk. Exploitation could allow attackers to execute arbitrary commands on the device, potentially leading to network reconnaissance, lateral movement, or disruption of network connectivity. Given the devices' role in bridging wireless networks, compromise could expose sensitive internal traffic or enable man-in-the-middle attacks. The lack of vendor response and patches increases exposure time, raising the likelihood of exploitation. Critical infrastructure or organizations with remote workforces using these devices may face increased risk of data breaches or operational disruption. Additionally, compromised devices could be leveraged as part of botnets or for launching further attacks within European networks.

Immediate mitigation should focus on network-level controls and device configuration hardening. Organizations should isolate Linksys range extenders from critical network segments using VLANs or firewall rules to limit exposure. Disable remote management interfaces if enabled, and restrict access to the /goform/setLan endpoint by IP filtering or network segmentation. Monitor network traffic for unusual patterns indicative of command injection attempts. Since no official patches are available, consider replacing affected devices with models from vendors providing timely security updates. For environments where replacement is not immediately feasible, implement strict network access controls and continuous monitoring. Additionally, inform users about the vulnerability and advise against exposing these devices directly to the internet. Regularly check for vendor updates or community patches and apply them promptly once available.