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CVE-2026-40854

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

CVSS 4.0 8.7 HIGHCheck source for fixed versionsKEV status unknown
Original advisory

cve-program · CVE-2026-40854

Published

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

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Affected versions, risk and source history

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Publishers link these advisories through the identifiers shown below. A shared identifier or date alone does not tell you whether your software is affected or whether the advisories describe the same cause.

CVE-2026-40854 · CVE overview and exploitation status

cve-program · CVE-2026-40854

Related changes

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ChangeIntel

An IT change radar: releases, security, known issues, retirements, documentation changes, and service status from public sources. Every item links to supporting evidence; dates and statuses can change after they are read.

Sources read 13 Nov 10:02 UTC · 274 of 275 readable · 272 fully read · documentation 469/469 current

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