CVE-2025-7434 is a critical stack-based buffer overflow vulnerability affecting the Tenda FH451 router firmware versions 1.0.0.0 through 1.0.0.9. The flaw exists in the POST request handler component, specifically within the fromAddressNat function located at /goform/addressNat. The vulnerability arises due to improper handling of the 'page' argument, which can be manipulated by an attacker to overflow the 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 prior authentication, increasing its risk profile. The CVSS 4.0 score is 8.7 (high severity), reflecting the ease of exploitation (network attack vector, low complexity) and the significant impact on confidentiality, integrity, and availability. Although no known exploits are currently observed in the wild, the public disclosure of the exploit code increases the likelihood of active exploitation. The vulnerability affects a widely deployed consumer and small office/home office (SOHO) router model, which is often used to provide network connectivity and NAT services. Successful exploitation could allow attackers to gain control over the device, intercept or manipulate network traffic, pivot into internal networks, or disrupt network availability.

For European organizations, this vulnerability poses a significant threat, especially for small and medium enterprises (SMEs) and home office setups that rely on Tenda FH451 routers for internet connectivity. Exploitation could lead to unauthorized network access, data interception, and potential lateral movement within corporate networks. This could compromise sensitive business information, disrupt operations, and degrade network performance. Additionally, the ability to execute arbitrary code on the router could allow attackers to install persistent malware or use the device as a launchpad for further attacks. Given the critical nature of the vulnerability and the lack of authentication requirements, attackers can remotely exploit vulnerable devices without user interaction, increasing the risk of widespread compromise. The impact extends to availability as well, since exploitation could cause router crashes or network outages, affecting business continuity. The exposure is heightened in remote work environments where security monitoring may be less stringent.

Organizations should immediately inventory their network infrastructure to identify any Tenda FH451 devices running affected firmware versions. Since no official patches or updates are currently linked, mitigation should focus on network-level controls: restrict remote access to router management interfaces by implementing firewall rules or VPN access; disable remote management features if not required; monitor network traffic for unusual POST requests targeting /goform/addressNat endpoints; implement intrusion detection/prevention systems (IDS/IPS) signatures to detect exploitation attempts; and consider network segmentation to isolate vulnerable devices from critical assets. Where possible, replace affected devices with updated models or firmware versions once patches become available. Additionally, educating users about the risks and encouraging prompt firmware updates when released will be critical. Vendors should be engaged to expedite patch development and distribution. Regular backups of router configurations and network monitoring logs will aid in incident response if exploitation occurs.