CVE-2026-40854: Wnc T-Mobile 5g Box Idu

High severity, CVSS 8.7. EPSS: 0.3% chance of exploitation in the next 30 days.

WNC T-Mobile 5G Box IDU router contains an authentication bypass vulnerability in the portal.cgi component. The session verification mechanism improperly validates the sessionid cookie by checking for the existence of a corresponding file in /tmp/login_user. An attacker can bypass authentication by using directory entries such as "." or ".." in the cookie, allowing unauthorized access to the administration panel.This issue has been fixed in firmware version 1.1.0.651412

Affected products

• Wnc T-Mobile 5g Box Idu: before 1.1.0.651412 (fixed in 1.1.0.651412)

Published 2026-09-16. Last modified 2026-09-28.