The vulnerability identified as CVE-2025-71026 affects the Tenda AX-3 router firmware version 16.03.12.10_CN. It is a stack-based buffer overflow located in the handling of the wanSpeed2 parameter within the fromAdvSetMacMtuWan function. This function is likely involved in configuring WAN interface parameters such as speed and MTU settings. An attacker can send a specially crafted request containing a malicious wanSpeed2 parameter value, which triggers the stack overflow, leading to memory corruption and ultimately causing the device to crash or reboot, resulting in a denial of service (DoS). The CVSS v3.1 base score is 7.5, reflecting a high severity due to the vulnerability's network attack vector (AV:N), low attack complexity (AC:L), no privileges required (PR:N), and no user interaction needed (UI:N). The impact is limited to availability (A:H), with no confidentiality (C:N) or integrity (I:N) impact. No known exploits have been reported in the wild, and no official patches have been released at the time of publication. The vulnerability is categorized under CWE-121, which corresponds to stack-based buffer overflows, a common and dangerous class of memory corruption bugs. This vulnerability could be exploited remotely by unauthenticated attackers, making it a significant risk for affected devices exposed to the internet or untrusted networks.

For European organizations, the primary impact of CVE-2025-71026 is the potential disruption of network connectivity due to router crashes caused by the stack overflow. This can lead to denial of service conditions affecting business operations, especially for small and medium enterprises relying on Tenda AX-3 routers for internet access or WAN connectivity. Although the vulnerability does not compromise data confidentiality or integrity, the loss of availability can interrupt critical services, remote work capabilities, and communication channels. In sectors such as finance, healthcare, and manufacturing, even short outages can have significant operational and financial consequences. Additionally, repeated exploitation attempts could increase network instability and complicate incident response efforts. The absence of known exploits in the wild currently reduces immediate risk, but the ease of exploitation and lack of authentication requirements mean that threat actors could develop and deploy exploits rapidly once discovered.

1. Immediately isolate Tenda AX-3 routers from untrusted networks or restrict WAN access using firewall rules to limit exposure to potential attackers. 2. Monitor network traffic for unusual or malformed requests targeting WAN configuration interfaces, especially those involving the wanSpeed2 parameter or related management protocols. 3. Implement network segmentation to separate critical systems from devices running vulnerable firmware to contain potential disruptions. 4. Regularly check for firmware updates or security advisories from Tenda and apply patches promptly once available. 5. If patching is delayed, consider replacing vulnerable devices with alternative routers from vendors with stronger security track records. 6. Employ intrusion detection/prevention systems (IDS/IPS) capable of detecting exploitation attempts targeting known buffer overflow patterns. 7. Educate IT staff about this vulnerability to ensure rapid identification and response to any incidents involving router instability or DoS symptoms. 8. Maintain backups of router configurations to enable quick recovery after forced reboots or crashes.