CVE-2025-46627 is a high-severity vulnerability affecting the Tenda RX2 Pro router firmware version 16.03.30.14. The vulnerability stems from the use of weak credentials for the device's telnet service, allowing an unauthenticated attacker to gain access by calculating the root password. The root password is derived from the last two digits or octets of the device's MAC address, which is easily obtainable information. This means that an attacker does not need prior authentication or user interaction to exploit this flaw. The vulnerability is classified under CWE-922, which relates to improper restriction of operations within the bounds of a memory buffer, but here it is more about weak credential generation. The CVSS v3.1 score is 8.2, indicating a high severity with network attack vector, low attack complexity, no privileges required, no user interaction, and high confidentiality impact but limited integrity and no availability impact. Exploiting this vulnerability would allow an attacker to authenticate to the telnet service as root, potentially enabling unauthorized access to the device’s configuration and network traffic, leading to further compromise of the internal network or interception of sensitive data. No patches or fixes have been published yet, and there are no known exploits in the wild at the time of publication. However, the ease of password derivation from the MAC address makes this vulnerability a significant risk for affected devices.

For European organizations, this vulnerability poses a substantial risk especially for those using Tenda RX2 Pro routers in their network infrastructure. Unauthorized telnet access as root could lead to full device compromise, allowing attackers to manipulate network configurations, intercept or redirect traffic, deploy malware, or use the device as a pivot point for lateral movement within the network. This could result in confidentiality breaches of sensitive corporate or personal data, disruption of network services, and potential regulatory non-compliance under GDPR if personal data is exposed. The lack of availability impact reduces the risk of denial-of-service, but the high confidentiality impact and ease of exploitation without authentication make it a critical concern. Organizations relying on these routers for home office setups or small branch offices may be particularly vulnerable if these devices are not segmented or monitored. The absence of patches increases the urgency for mitigation measures to prevent exploitation.

Given the absence of official patches, European organizations should take immediate practical steps to mitigate this vulnerability. First, disable the telnet service on all Tenda RX2 Pro devices if possible, replacing it with more secure management protocols such as SSH with strong authentication. If telnet cannot be disabled, restrict access to the telnet port via firewall rules to trusted management networks only. Network segmentation should be enforced to isolate vulnerable devices from critical infrastructure and sensitive data. Monitoring and logging of telnet access attempts should be enabled to detect potential exploitation attempts. Organizations should inventory their network devices to identify any Tenda RX2 Pro routers and consider replacing them with devices from vendors with better security track records. Additionally, changing the MAC address (MAC spoofing) to disrupt the predictable password derivation could be a temporary workaround, though this may not be feasible in all environments. Finally, organizations should stay alert for any patch releases or vendor advisories and apply updates promptly once available.