CVE-2026-40854
High
Description
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
SeverityHigh
CVSS8.7
Exploit probability—
ProductT-Mobile 5G Box IDU
PublishedSep 16, 2026
First seenSep 16, 2026
Weakness typeCWE-290CWE-290
How to fix
Update
- WNC T-Mobile 5G Box IDU1.1.0.651412 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| WNC T-Mobile 5G Box IDU | v < 1.1.0.651412 | 1.1.0.651412 |
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