CVE-2025-9525 is a high-severity stack-based buffer overflow vulnerability found in the Linksys E1700 router, specifically version 1.0.0.4.003. The flaw exists in the setWan function within the /goform/setWan endpoint. This vulnerability arises due to improper handling of the DeviceName or lanIp arguments, which allows an attacker to overflow the stack buffer remotely. Because this flaw can be triggered via network access without requiring user interaction or prior authentication, it presents a significant risk. The buffer overflow could enable an attacker to execute arbitrary code with elevated privileges on the device, potentially leading to full compromise of the router. The vulnerability has a CVSS 4.0 base score of 8.7, indicating high severity, with metrics showing network attack vector, low attack complexity, no privileges or user interaction required, and high impact on confidentiality, integrity, and availability. Although the vendor was notified early, no response or patch has been issued, and while no exploits are currently known to be in the wild, a public exploit has been published, increasing the likelihood of exploitation. This vulnerability threatens the security and stability of affected Linksys E1700 devices, which are commonly used in home and small office environments, potentially allowing attackers to intercept or manipulate network traffic, disrupt connectivity, or use the compromised device as a foothold for further attacks within a network.

For European organizations, this vulnerability poses a substantial risk, especially for small and medium enterprises (SMEs) and home offices relying on Linksys E1700 routers for internet connectivity. Successful exploitation could lead to unauthorized access to internal networks, interception of sensitive data, and disruption of business operations due to network outages or device instability. Given the high impact on confidentiality, integrity, and availability, attackers could manipulate routing configurations, redirect traffic to malicious endpoints, or launch further attacks such as lateral movement or data exfiltration. The lack of vendor response and patch availability exacerbates the risk, as organizations may remain exposed for extended periods. Additionally, the public availability of an exploit increases the threat landscape, making opportunistic attacks more likely. European organizations with remote or hybrid work setups that depend on these routers are particularly vulnerable, as attackers can exploit the flaw remotely without user interaction or credentials.

Immediate mitigation steps include isolating affected Linksys E1700 devices from critical network segments and restricting remote access to the router’s management interfaces via firewall rules or VPNs. Network administrators should monitor network traffic for unusual activity indicative of exploitation attempts, such as unexpected outbound connections or anomalous configuration changes. Since no official patch is available, organizations should consider replacing affected devices with updated models or alternative routers from vendors with active security support. Employing network segmentation to limit the impact of a compromised device and implementing intrusion detection/prevention systems (IDS/IPS) tuned to detect buffer overflow exploit patterns targeting /goform/setWan can further reduce risk. Additionally, organizations should maintain up-to-date asset inventories to identify vulnerable devices promptly and educate users about the risks of using unsupported or unpatched network equipment. Regular backups of router configurations and network settings can aid in rapid recovery if compromise occurs.