CVE-2025-52364 is a security vulnerability identified in the firmware of the Tenda CP3 Pro router, specifically version V22.5.4.93. The vulnerability arises from insecure permissions that cause the telnet service (telnetd) to be enabled by default at device boot through the initialization script located at /etc/init.d/eth.sh. Telnet is an unencrypted protocol that allows remote command-line access to the device. Because the service is enabled by default, remote attackers can potentially connect to the router's shell interface over the network. The risk is further exacerbated if the device is configured with default or weak credentials, as attackers could gain unauthorized access without needing to bypass authentication mechanisms. This vulnerability exposes the device to remote code execution and full control by attackers, enabling them to manipulate network traffic, install malware, or pivot to other internal systems. Although no known exploits are currently reported in the wild, the presence of an open telnet service with weak or default credentials is a critical security weakness that can be easily exploited by attackers scanning for vulnerable devices. The lack of a CVSS score indicates that the vulnerability is newly published and may not yet have been fully assessed, but the technical details clearly indicate a high-risk scenario due to the combination of default enabled remote access and weak authentication controls.

For European organizations, this vulnerability poses a significant threat, especially for small and medium enterprises or home office environments that commonly use consumer-grade routers like the Tenda CP3 Pro. Compromise of these devices can lead to unauthorized network access, interception of sensitive data, and disruption of network availability. Attackers gaining shell access could alter device configurations, redirect traffic to malicious servers, or create persistent backdoors. This could result in data breaches, loss of confidentiality, and potential lateral movement within corporate networks. Given the widespread use of Tenda routers in residential and small business markets across Europe, the vulnerability could be exploited to launch large-scale botnet attacks or targeted intrusions. Additionally, critical infrastructure or organizations with remote sites using these devices may face operational disruptions. The unencrypted nature of telnet also increases the risk of credential interception on local networks, compounding the threat. Overall, the vulnerability undermines network perimeter security and could facilitate broader cyberattacks affecting European organizations' confidentiality, integrity, and availability.

To mitigate this vulnerability, European organizations should first verify if they are using the Tenda CP3 Pro router with firmware version V22.5.4.93 or similar. Immediate steps include disabling the telnet service on the device, either through the router's administrative interface or by applying configuration changes to prevent the /etc/init.d/eth.sh script from enabling telnet at boot. If disabling telnet is not possible, changing default credentials to strong, unique passwords is critical to prevent unauthorized access. Network segmentation should be employed to isolate vulnerable devices from sensitive internal networks. Organizations should also monitor network traffic for unusual telnet connections and implement intrusion detection systems to alert on suspicious activity. Firmware updates should be applied as soon as Tenda releases a patched version addressing this issue. Where possible, replacing vulnerable devices with more secure alternatives that do not enable telnet by default is advisable. Additionally, organizations should educate users about the risks of default credentials and encourage regular password updates. Finally, restricting remote management access to trusted IP addresses or VPN connections can reduce exposure to external attackers.