CVE-2025-55603 is a buffer overflow vulnerability identified in the Tenda AX3 router firmware version V16.03.12.10_CN. The flaw exists in the fromSetSysTime function, which processes the ntpServer parameter. Buffer overflow vulnerabilities occur when a program writes more data to a buffer than it can hold, potentially overwriting adjacent memory. In this case, improper validation or sanitization of the ntpServer input allows an attacker to overflow the buffer, which can lead to arbitrary code execution, denial of service, or system instability. Given that the vulnerability resides in a network time protocol (NTP) related function, exploitation could be triggered remotely by sending specially crafted requests to the router's interface that handles NTP server configuration or synchronization. Although no known exploits are currently reported in the wild, the nature of buffer overflow vulnerabilities in network-facing devices makes this a significant risk. The absence of a CVSS score indicates that the vulnerability is newly published and has not yet been fully assessed or assigned a severity rating. The affected version is specifically the Chinese firmware release V16.03.12.10_CN, but it is unclear if other regional firmware versions or subsequent updates are impacted. The vulnerability could allow attackers to gain elevated privileges on the router, potentially compromising the confidentiality and integrity of network traffic passing through the device, as well as impacting availability by causing crashes or reboots.

For European organizations, the impact of this vulnerability could be substantial, especially for those using Tenda AX3 routers or similar devices in their network infrastructure. Compromise of a router can lead to interception or manipulation of sensitive data, disruption of network services, and establishment of persistent footholds for further attacks. In enterprise or critical infrastructure environments, this could result in data breaches, operational downtime, and loss of trust. Small and medium-sized businesses that rely on consumer-grade routers like the Tenda AX3 may be particularly vulnerable due to less rigorous network security controls. Additionally, routers are often a single point of failure and a gateway to internal networks, so exploitation could facilitate lateral movement by attackers. Given the router’s role in managing network time synchronization, manipulation of NTP settings could also disrupt time-dependent security mechanisms such as logging, authentication, and certificate validation, further complicating incident response and forensic investigations.

Organizations should immediately verify if they are using the Tenda AX3 router with the affected firmware version V16.03.12.10_CN. If so, they should seek firmware updates or patches from Tenda as soon as they become available. In the absence of an official patch, it is advisable to disable remote management interfaces and restrict access to the router’s configuration interface to trusted internal networks only. Network segmentation should be employed to isolate critical systems from devices that may be vulnerable. Monitoring network traffic for unusual NTP requests or configuration changes can help detect exploitation attempts. Additionally, organizations should consider replacing affected routers with models from vendors that provide timely security updates and have a strong security track record. Applying strict input validation and employing intrusion detection/prevention systems that can identify buffer overflow attack patterns targeting network devices can also reduce risk. Regularly auditing network devices and maintaining an up-to-date asset inventory will facilitate rapid response to emerging vulnerabilities.