CVE-2026-40854

Session auth bypass via cookie value in T-Mobile 5G Box IDU routers

Published Sep 16, 2026 CVSS 4.0 · 8.7 High EPSS < 1% KEV · Not listed
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

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

No advisories available
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}

Type Values Removed Values Added
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
Title Session auth bypass via cookie value in T-Mobile 5G Box IDU routers
First Time appeared Wnc
Wnc t-mobile 5g Box Idu
Weaknesses CWE-290
CPEs cpe:2.3:a:wnc:t-mobile_5g_box_idu:*:*:*:*:*:*:*:*
Vendors & Products Wnc
Wnc t-mobile 5g Box Idu
References
Metrics cvssV4_0

{'score': 8.7, 'vector': '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'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
CERT-PL
Published
Updated
Sep 16, 2026, 5:41 PM
Reserved
Apr 15, 2026, 11:10 AM
Status
Awaiting Analysis
Published
Sep 16, 2026, 12:17 PM
Modified
Sep 28, 2026, 11:10 PM