CVE-2025-9526 is a high-severity stack-based buffer overflow vulnerability affecting the Linksys E1700 router running firmware version 1.0.0.4.003. The vulnerability resides in the setSysAdm function within the /goform/setSysAdm endpoint. Specifically, the issue arises from improper handling of the rm_port argument, which can be manipulated by an attacker to overflow a stack buffer. This overflow can lead to arbitrary code execution or cause the device to crash, resulting in denial of service. The vulnerability is remotely exploitable without requiring user interaction or authentication, making it particularly dangerous. The CVSS 4.0 base score is 8.7, reflecting its high impact on confidentiality, integrity, and availability. The vendor, Linksys, was notified early but has not responded or released a patch, and a public exploit has been disclosed, increasing the risk of exploitation. Although no known exploits in the wild have been reported yet, the public availability of exploit code significantly raises the threat level. This vulnerability affects a widely used consumer-grade router, which is often deployed in home and small office environments, potentially exposing many users to compromise. The lack of vendor response and patch availability means that affected devices remain vulnerable, and attackers can leverage this flaw to gain control over the router, intercept or manipulate network traffic, or disrupt network connectivity.

For European organizations, the impact of CVE-2025-9526 can be substantial, especially for small and medium-sized enterprises (SMEs) and home offices that rely on Linksys E1700 routers for network connectivity. Successful exploitation could allow attackers to execute arbitrary code on the router, leading to full compromise of the device. This could enable interception of sensitive data, insertion of malicious payloads into network traffic, or pivoting into internal networks, thereby threatening confidentiality and integrity. Additionally, exploitation could cause denial of service by crashing the router, impacting availability and business continuity. Given the router’s role as a network gateway, compromise could facilitate broader attacks against organizational IT infrastructure. The absence of a vendor patch and the public availability of exploit code increase the likelihood of attacks targeting European networks, potentially affecting critical communications and data flows. Organizations with limited IT security resources may be particularly vulnerable, as they might not have the capability to detect or mitigate such attacks promptly.

1. Immediate mitigation should focus on isolating affected Linksys E1700 devices from critical network segments to limit potential damage. 2. Network administrators should monitor network traffic for unusual activity originating from or targeting the router, including unexpected connections to the /goform/setSysAdm endpoint. 3. Implement network-level access controls to restrict remote access to router management interfaces, ideally limiting access to trusted IP addresses or internal networks only. 4. Where possible, replace affected Linksys E1700 routers with alternative devices that have received security updates or are not vulnerable to this issue. 5. Employ network intrusion detection/prevention systems (IDS/IPS) with signatures tuned to detect exploitation attempts targeting this vulnerability. 6. Regularly audit and update router configurations to disable unnecessary services and management interfaces exposed to the internet. 7. Educate users and administrators about the risks of using outdated firmware and the importance of timely updates, even if vendor support is lacking. 8. Consider deploying compensating controls such as VPNs or firewall rules to protect network traffic and management access until a patch or device replacement is feasible.