CVE-2025-71027 identifies a stack overflow vulnerability in the Tenda AX-3 router firmware version 16.03.12.10_CN, specifically within the wanMTU2 parameter processed by the fromAdvSetMacMtuWan function. This vulnerability arises from improper handling of input data leading to a stack-based buffer overflow (CWE-121). An attacker can send a specially crafted request targeting the wanMTU2 parameter, triggering the overflow and causing the router to crash or reboot, resulting in a denial of service (DoS) condition. The vulnerability is remotely exploitable without any authentication or user interaction, as indicated by the CVSS vector (AV:N/AC:L/PR:N/UI:N). The impact is limited to availability disruption; confidentiality and integrity are not affected. Although no exploits have been observed in the wild and no official patches have been released, the high CVSS score (7.5) reflects the ease of exploitation and significant potential for service interruption. The affected product, Tenda AX-3, is a consumer-grade Wi-Fi 6 router widely used in various regions, including parts of Europe. The lack of patches and public exploit code necessitates proactive defensive measures to mitigate potential attacks.

For European organizations, the primary impact of CVE-2025-71027 is the potential for network outages caused by denial of service attacks on Tenda AX-3 routers. This can disrupt internet connectivity, impair business operations, and affect services reliant on continuous network availability. Organizations using these routers in critical infrastructure, small to medium enterprises, or home office environments may experience operational downtime. The vulnerability does not compromise data confidentiality or integrity but can degrade service reliability. Given the remote and unauthenticated nature of the exploit, attackers can target exposed WAN interfaces from anywhere, increasing the risk of widespread disruption. The absence of known exploits in the wild currently limits immediate risk, but the availability of technical details may facilitate future exploit development. European entities with limited IT security resources or those that have not segmented their networks may be particularly vulnerable to cascading effects from router outages.

1. Immediately restrict WAN-side access to router management interfaces to prevent remote exploitation. 2. Implement network segmentation to isolate critical systems from consumer-grade routers like the Tenda AX-3. 3. Monitor network traffic for unusual or malformed packets targeting the wanMTU2 parameter or related management functions. 4. Disable remote management features on affected routers if not strictly necessary. 5. Regularly check for firmware updates from Tenda and apply patches promptly once available. 6. Consider replacing vulnerable Tenda AX-3 devices with routers from vendors with stronger security track records if patching is delayed. 7. Employ intrusion detection/prevention systems (IDS/IPS) capable of detecting attempts to exploit stack overflow patterns. 8. Educate IT staff about this vulnerability to ensure rapid response to any signs of exploitation or service disruption.