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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

Read the publisher's advisory

Affected versions, risk and source history

cve-program · CVE-2026-40854

Published

T-Mobile 5G Box IDU

Vendor product

Publisher's version information

Shown as published. These rules are not interpreted as NuGet package version ranges.

{
                    "vendor": "WNC",
                    "product": "T-Mobile 5G Box IDU",
                    "versions": [
                        {
                            "status": "affected",
                            "version": "0",
                            "lessThan": "1.1.0.651412",
                            "versionType": "custom"
                        }
                    ],
                    "defaultStatus": "unaffected"
                }

Original source record · Cite this exact observation · Complete original publisher JSON