CVE-2025-43986 is a vulnerability identified in KuWFi GC111 GC111-GL-LM321_V3.0_20191211 devices, where the TELNET service is enabled by default and exposed directly over the WAN interface without any authentication mechanism. TELNET is an outdated and insecure protocol that transmits data, including credentials, in plaintext, making it highly susceptible to interception and unauthorized access. The exposure of TELNET on the WAN interface means that any attacker on the internet can connect to these devices remotely without needing credentials, gaining direct access to the device's command line interface. This can allow attackers to execute arbitrary commands, potentially leading to full device compromise, network pivoting, data exfiltration, or the device being recruited into botnets. The lack of authentication combined with WAN exposure significantly increases the attack surface and risk. Although no known exploits are currently reported in the wild, the vulnerability presents a critical risk due to the ease of exploitation and the sensitive nature of network devices. The affected devices appear to be specific KuWFi models, which are likely used as network gateways or IoT hubs. The absence of a CVSS score suggests this is a newly published vulnerability, but the technical details clearly indicate a severe security flaw.

For European organizations, this vulnerability poses a significant risk, especially for small to medium enterprises or residential users relying on KuWFi GC111 devices for internet connectivity. Compromise of these devices could lead to unauthorized network access, interception of internal communications, and lateral movement within corporate networks. This could result in data breaches, disruption of business operations, and potential regulatory non-compliance under GDPR if personal data is exposed. Additionally, compromised devices could be used as entry points for launching attacks against other internal or external targets, amplifying the threat. The exposure of TELNET on WAN also increases the likelihood of automated scanning and exploitation by cybercriminals or state-sponsored actors targeting vulnerable network infrastructure in Europe.

Immediate mitigation steps include disabling the TELNET service on all affected KuWFi GC111 devices, especially on the WAN interface. If disabling TELNET is not possible due to device limitations, network administrators should implement strict firewall rules to block inbound TELNET (TCP port 23) traffic from untrusted networks. It is critical to update the device firmware if a patch becomes available from the vendor. Network segmentation should be enforced to isolate vulnerable devices from critical infrastructure. Additionally, organizations should monitor network traffic for unusual TELNET connections and implement intrusion detection systems to alert on suspicious activity. Where possible, replace TELNET with secure management protocols such as SSH with strong authentication. Finally, organizations should conduct asset inventories to identify all affected devices and prioritize remediation accordingly.