CVE-2025-8820 is a high-severity stack-based buffer overflow 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 wirelessBasic function, specifically in the /goform/wirelessBasic endpoint, where improper handling of the 'submit_SSID1' argument allows an attacker to overflow the stack buffer. This overflow can be triggered remotely without authentication or user interaction, enabling an attacker to execute arbitrary code or cause a denial of service on the affected device. The vulnerability has been publicly disclosed, and although the vendor was notified early, no response or patch has been issued to date. The CVSS 4.0 base score of 8.7 reflects the critical nature of this flaw, with network attack vector, low attack complexity, no privileges or user interaction required, and high impact on confidentiality, integrity, and availability. Exploitation could allow attackers to gain control over the device, manipulate network traffic, or pivot into internal networks, posing significant risks especially in environments relying on these devices for wireless connectivity.

For European organizations, the impact of this vulnerability can be substantial. Linksys range extenders are commonly used in both enterprise and home office environments to extend wireless coverage. Compromise of these devices can lead to unauthorized network access, interception or manipulation of sensitive data, and disruption of wireless services. In sectors such as finance, healthcare, and critical infrastructure, where secure and reliable network connectivity is essential, exploitation could result in data breaches, operational downtime, and regulatory non-compliance. Additionally, compromised devices could be leveraged as footholds for lateral movement within corporate networks or as part of botnets for broader attacks. The lack of vendor response and patches increases the window of exposure, making timely mitigation critical to reduce risk.

Given the absence of official patches, European organizations should implement immediate compensating controls. These include isolating affected Linksys extenders on segmented network zones with strict access controls to limit exposure. Disable remote management interfaces and restrict access to the /goform/wirelessBasic endpoint via firewall rules or network filtering. Regularly monitor network traffic for anomalous activity indicative of exploitation attempts. Where feasible, replace vulnerable devices with models from vendors providing timely security updates. Employ network intrusion detection systems (NIDS) with signatures for known exploit attempts targeting this vulnerability. Additionally, enforce strong wireless security policies and conduct regular security assessments to identify and remediate potential weaknesses. Organizations should also maintain an inventory of affected devices to prioritize mitigation efforts and prepare for patch deployment once available.