The vulnerability identified as CVE-2025-71020 affects the Tenda AX-1806 router running firmware version 1.0.0.1. It is a stack overflow vulnerability located in the sub_4C408 function, specifically within the processing of a security parameter. Stack overflow vulnerabilities occur when a program writes more data to a buffer located on the stack than it can hold, which can overwrite adjacent memory and cause unpredictable behavior. In this case, the crafted request exploits this overflow to cause the router to crash or become unresponsive, resulting in a Denial of Service (DoS). The vulnerability does not require user authentication, meaning an attacker with network access to the device can exploit it remotely. There is no indication of code execution or privilege escalation, limiting the impact to availability. No patches or fixes have been released at the time of publication, and no exploits have been observed in the wild. The lack of a CVSS score suggests the vulnerability is newly disclosed and not yet fully assessed. The affected device is commonly used in consumer and small business environments, which may have limited security monitoring and patch management capabilities. Attackers could leverage this vulnerability to disrupt network services, impacting business operations or home connectivity.

For European organizations, the primary impact of CVE-2025-71020 is disruption of network availability due to router crashes. This can lead to loss of internet connectivity, interruption of business communications, and potential downtime for services relying on the affected routers. Small and medium enterprises (SMEs) and home offices using Tenda AX-1806 devices are particularly vulnerable, as these environments often lack redundant network infrastructure or rapid incident response capabilities. In sectors where continuous connectivity is critical, such as finance, healthcare, or remote work setups, even short outages can have significant operational and financial consequences. Additionally, denial of service attacks can be used as a distraction or precursor to other attacks, increasing the overall risk profile. Since no known exploits are in the wild, the immediate threat level is moderate, but the lack of patches means the vulnerability remains open to future exploitation. European organizations should be aware of this risk and take proactive measures to mitigate potential disruptions.

1. Monitor Tenda’s official channels for firmware updates addressing CVE-2025-71020 and apply patches promptly once available. 2. Restrict network access to the router’s management interfaces by implementing network segmentation and firewall rules to limit exposure to untrusted networks. 3. Disable remote management features if not required, reducing the attack surface. 4. Employ network monitoring tools to detect unusual traffic patterns or repeated malformed requests targeting the router. 5. For critical environments, consider deploying redundant network paths or failover devices to maintain connectivity in case of device failure. 6. Educate IT staff and users about the vulnerability and encourage reporting of connectivity issues that may indicate exploitation attempts. 7. If feasible, replace affected devices with models from vendors with stronger security track records and active patch support.