CVE-2025-71020 identifies a stack-based buffer overflow vulnerability in the Tenda AX-1806 router firmware version 1.0.0.1, specifically within the sub_4C408 function that processes a security parameter. The vulnerability arises from improper bounds checking on the input, allowing an attacker to overflow the stack by sending a crafted network request. This overflow leads to a denial of service (DoS) condition by crashing the device, rendering it unavailable to legitimate users. The flaw requires no authentication or user interaction and can be exploited remotely over the network, increasing its risk profile. The vulnerability is categorized under CWE-121, indicating a classic stack overflow issue. The CVSS v3.1 base score of 7.5 reflects a high severity due to the network attack vector (AV:N), low attack complexity (AC:L), no privileges required (PR:N), no user interaction (UI:N), unchanged scope (S:U), no impact on confidentiality or integrity (C:N/I:N), but high impact on availability (A:H). No patches or mitigations have been officially released by the vendor as of the publication date, and no known exploits are currently in the wild. However, the potential for disruption in environments relying on this router model is significant, especially in enterprise or critical infrastructure contexts. The vulnerability highlights the importance of secure input validation in embedded device firmware to prevent service outages.

For European organizations, exploitation of CVE-2025-71020 could lead to denial of service on affected Tenda AX-1806 routers, disrupting network connectivity and potentially impacting business operations, especially in environments where these devices serve as primary gateways or are part of critical infrastructure. The loss of availability could affect internal communications, internet access, and connected services, leading to operational downtime and potential financial losses. Since the vulnerability does not affect confidentiality or integrity, data breaches are unlikely, but the service disruption alone can have cascading effects on productivity and incident response capabilities. Organizations with remote or unmanaged deployments of these routers are at higher risk, as attackers can exploit the vulnerability without authentication. The absence of a patch increases exposure duration, necessitating interim protective measures. The impact is more pronounced in sectors with stringent uptime requirements such as healthcare, finance, and public services within Europe.

1. Immediately inventory and identify all Tenda AX-1806 routers in your network environment to assess exposure. 2. Restrict network access to router management interfaces by implementing firewall rules and network segmentation to limit exposure to untrusted networks. 3. Monitor vendor communications closely for firmware updates or patches addressing CVE-2025-71020 and apply them promptly once available. 4. Employ network intrusion detection/prevention systems (IDS/IPS) to detect and block suspicious crafted requests targeting the vulnerable function. 5. Consider temporary replacement or isolation of affected devices in critical network segments until a patch is released. 6. Conduct regular network traffic analysis to identify anomalous patterns indicative of exploitation attempts. 7. Educate network administrators about the vulnerability and recommended security practices to prevent accidental exposure. 8. Implement robust backup and recovery procedures to minimize downtime impact in case of successful exploitation.