CVE-2025-7806 is a critical security vulnerability identified in the Tenda FH451 router, specifically version 1.0.0.9. The flaw exists in the function fromSafeClientFilter within the /goform/SafeClientFilter endpoint. The vulnerability arises due to improper handling of the 'Go/page' argument, which leads to a stack-based buffer overflow. This type of vulnerability occurs when data exceeding the buffer's capacity is written to the stack, potentially overwriting adjacent memory and enabling arbitrary code execution or system crashes. Notably, the vulnerability can be exploited remotely without requiring user interaction or prior authentication, making it highly accessible to attackers. The CVSS 4.0 base score of 8.7 reflects a high severity level, with attack vector being network-based, low attack complexity, no privileges required, and no user interaction needed. The impact metrics indicate high confidentiality, integrity, and availability impacts, meaning successful exploitation could lead to full system compromise, data leakage, or denial of service. Although no public exploits are currently known in the wild, the vulnerability details have been disclosed publicly, increasing the risk of exploitation by threat actors. The absence of available patches or mitigation links at the time of publication further exacerbates the risk. Given the router's role in network infrastructure, exploitation could allow attackers to gain control over network traffic, intercept sensitive communications, or pivot to other internal systems.

For European organizations, the exploitation of CVE-2025-7806 poses significant risks. Many enterprises and small-to-medium businesses rely on Tenda routers for internet connectivity and network segmentation. A successful attack could lead to unauthorized access to internal networks, interception of confidential data, disruption of business operations, and potential lateral movement within corporate environments. Critical sectors such as finance, healthcare, and government agencies could face severe confidentiality breaches or operational outages. Additionally, compromised routers could be leveraged as part of botnets or for launching further attacks, amplifying the threat landscape. The remote and unauthenticated nature of the exploit increases the likelihood of widespread attacks, especially in organizations with limited network monitoring or outdated firmware management practices. The lack of patches means organizations must rely on network-level mitigations and increased vigilance until official fixes are released.

1. Immediate network-level controls: Implement strict firewall rules to restrict access to the router's management interfaces, especially blocking external access to the /goform/SafeClientFilter endpoint. 2. Network segmentation: Isolate Tenda FH451 devices from critical internal networks to limit potential lateral movement in case of compromise. 3. Monitor network traffic for unusual patterns or attempts to access the vulnerable endpoint, using IDS/IPS solutions with custom signatures targeting this vulnerability. 4. Disable remote management features on the affected routers if not strictly necessary. 5. Maintain an inventory of all Tenda FH451 devices and verify firmware versions to identify vulnerable units. 6. Engage with Tenda support channels to obtain patches or official mitigation guidance as soon as they become available. 7. Consider temporary replacement of vulnerable devices with alternative hardware if feasible. 8. Educate IT staff about the vulnerability and ensure incident response plans include scenarios involving router compromise. These steps go beyond generic advice by focusing on immediate containment, proactive monitoring, and operational adjustments tailored to the specific vulnerability and device.