CVE-2025-9481 is a high-severity stack-based buffer overflow vulnerability affecting multiple Linksys range extender models, including RE6250, RE6300, RE6350, RE6500, RE7000, and RE9000, across firmware versions 1.0.013.001, 1.0.04.001, 1.0.04.002, 1.1.05.003, and 1.2.07.001. The vulnerability resides in the setIpv6 function within the /goform/setIpv6 endpoint. Specifically, the flaw is triggered by manipulating the tunrd_Prefix argument, which leads to a stack-based buffer overflow condition. This type of vulnerability can allow an attacker to overwrite critical memory regions on the device, potentially enabling arbitrary code execution or causing denial of service. The vulnerability is remotely exploitable without requiring user interaction or authentication, as indicated by the CVSS vector (AV:N/AC:L/AT:N/UI:N/PR:L). The CVSS 4.0 base score is 8.7, reflecting a high severity due to the ease of exploitation and the potential for significant impact on confidentiality, integrity, and availability. Although the vendor was notified early, no response or patch has been issued, and public exploit code has been disclosed, increasing the risk of exploitation. The vulnerability affects the core networking functionality related to IPv6 configuration, which is critical for device operation and network security. Exploitation could allow attackers to gain control over the device, intercept or manipulate network traffic, or disrupt network connectivity.

For European organizations, this vulnerability poses a substantial risk, especially for enterprises and service providers relying on Linksys range extenders to enhance wireless coverage. Compromise of these devices can lead to unauthorized network access, interception of sensitive data, lateral movement within internal networks, and disruption of network services. Given the remote exploitability without authentication, attackers can target vulnerable devices over the internet or internal networks. This is particularly concerning for organizations with distributed networks or remote offices using these extenders. The lack of vendor response and patches increases the window of exposure, potentially leading to widespread exploitation. Critical infrastructure, government agencies, and businesses handling sensitive data in Europe could face confidentiality breaches, operational disruptions, and reputational damage if attackers leverage this flaw. Additionally, compromised devices could be enlisted into botnets or used as pivot points for further attacks, amplifying the threat landscape.

Immediate mitigation steps include isolating affected Linksys extenders from critical network segments and disabling IPv6 configuration via the vulnerable endpoint if possible. Network administrators should monitor traffic to and from these devices for unusual activity, especially requests targeting /goform/setIpv6. Deploying network-level protections such as Web Application Firewalls (WAFs) or Intrusion Prevention Systems (IPS) with custom rules to detect and block exploit attempts targeting the tunrd_Prefix parameter is recommended. Organizations should inventory all Linksys extenders to identify affected models and firmware versions and plan for device replacement or firmware rollback if no patches are available. Employ network segmentation to limit exposure of vulnerable devices and restrict management interfaces to trusted networks only. Regularly update network device inventories and monitor vendor communications for any forthcoming patches or advisories. In the absence of vendor patches, consider deploying compensating controls such as VPNs or secure tunnels to protect management traffic and reduce attack surface. Finally, conduct security awareness training to inform IT staff about this vulnerability and encourage vigilance for related indicators of compromise.