A hidden feature in NEC Aterm routers allows an attacker to activate the Telnet service through network traffic. Turning on Telnet exposes a remote command interface that is normally disabled, potentially creating a vector for unauthorized control of the device. The flaw itself is a Remote Service Activation weakness classified as CWE‑912.

NEC Platforms, Ltd. Aterm Series routers and gateways, including models W1200EX(-MS), WF1200CR, WG1200CR, WG1200HP2, WG1200HP3, WG1200HP4, WG1200HS2, WG1200HS3, WG1200HS4, WG1800HP3, WG1800HP4, WG1900HP, WG1900HP2, WG2600HM4, WG2600HP4, WG2600HS, WG2600HS2, WX1500HP, WX3000HP, WX3000HP2, and WX3600HP. No firmware version is specified, so all updates of these models may carry the vulnerability until the vendor issues a corrective release.

The CVSS score of 6.3 indicates moderate severity, implying that activating Telnet can compromise device integrity or confidentiality. Exploit probability data is not provided, and the vulnerability is not listed in the CISA KEV catalog, suggesting no public exploitation has been documented. The likely attack vector is remote over the network, meaning any device exposed to the Internet or an untrusted internal network could be targeted to toggle Telnet on.