CVE-2025-70646 identifies a stack-based buffer overflow vulnerability in the Tenda AX1803 router firmware version 1.0.0.1. The vulnerability resides in the sub_72290 function, specifically in the handling of a security parameter, where improper bounds checking allows an attacker to overflow the stack. This flaw can be triggered remotely by sending a specially crafted network request to the device, causing it to crash and thus resulting in a denial of service (DoS). The vulnerability does not require any authentication or user interaction, and the attack vector is network-based, meaning an attacker can exploit it over the internet or local network. The CVSS v3.1 base score is 7.5, reflecting high severity due to the ease of exploitation and the impact on availability, though confidentiality and integrity remain unaffected. No patches or firmware updates have been released at the time of publication, and no known exploits have been observed in the wild. The vulnerability is classified under CWE-121 (Stack-based Buffer Overflow), a common and well-understood software weakness. Given the nature of the device—a consumer-grade router—this vulnerability could disrupt internet connectivity for users and potentially impact network availability in small business or home office environments where these routers are deployed.

The primary impact of CVE-2025-70646 is the denial of service caused by the router crashing due to the stack overflow. For European organizations, especially small and medium enterprises (SMEs) and home offices relying on Tenda AX1803 routers, this could lead to loss of internet connectivity, disruption of business operations, and potential downtime. Critical services dependent on continuous network availability could be interrupted, affecting productivity and possibly causing financial losses. Although the vulnerability does not compromise data confidentiality or integrity, the availability impact can be significant in environments with limited IT support or where these routers serve as the main gateway. Additionally, if exploited at scale, this vulnerability could be leveraged in coordinated attacks to disrupt multiple organizations or residential users simultaneously. The lack of available patches increases the risk window, necessitating immediate mitigation efforts. European sectors with high reliance on consumer-grade networking equipment, such as remote workers, small offices, and certain public institutions, may be disproportionately affected.

Since no official patches or firmware updates are currently available for this vulnerability, affected organizations should implement the following mitigations: 1) Immediately isolate Tenda AX1803 routers from untrusted networks, especially the internet, by placing them behind firewalls or network segmentation to limit exposure. 2) Disable any unnecessary remote management features or services on the router to reduce the attack surface. 3) Monitor network traffic for unusual or malformed packets targeting the router to detect potential exploitation attempts. 4) Where feasible, replace Tenda AX1803 devices with alternative routers from vendors with active security support and patch availability. 5) Implement network-level intrusion prevention systems (IPS) that can detect and block exploit attempts targeting this vulnerability. 6) Educate users about the risk and encourage prompt reporting of connectivity issues that may indicate exploitation. 7) Maintain up-to-date network device inventories to quickly identify and remediate vulnerable devices. These steps go beyond generic advice by focusing on network isolation, monitoring, and device replacement strategies tailored to the specific vulnerability and device type.