CVE-2026-40854
Session auth bypass via cookie value in T-Mobile 5G Box IDU routers
- State
- Published
- Severity
- 8.7 High
- Published
- Sep 16, 2026
- Updated
- Sep 16, 2026
- Reserved
- Apr 15, 2026
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
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 4.0 | 8.7 High | CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N | CERT-PL |
Weaknesses
- CWE-290 Authentication bypass by spoofing
Affected Products
| Product | Versions |
|---|---|
T-Mobile 5G Box IDUWNC |
|
References
- https://cert.pl/posts/2026/09/CVE-2026-40854third-party-advisory
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