CVE-2026-40854 — Session auth bypass via cookie value in T-Mobile 5G Box IDU routers
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…
Published: 2026-09-16 · CVSS: 8.7 · CVSS 4.0
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
Source: CVE Program · Revision 8b16575c39f1e1810c5e863010da073d2d3285e7