Session auth bypass via cookie value in T-Mobile 5G Box IDU routers (CVE-2026-40854) | HOL Guard CVE

Unknown severity · Source severity not reportedCVE-2026-40854

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

Answer in brief

CVE-2026-40854 records a Unknown severity vulnerability in Session auth bypass via cookie value in T-Mobile 5G Box IDU routers. The current sources do not mark it as known exploited. The current feed maps WNC/T-Mobile 5G Box IDU (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Sep 16, 2026Updated Sep 16, 2026Source checked Sep 16, 2026First seen by HOL Sep 16, 2026Material review Sep 16, 2026

Upstream Advisory

Key facts

Risk: Unknown severitySource severity not reported
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Available

Why this deserves its current priority

A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps WNC/T-Mobile 5G Box IDU (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
WNC/T-Mobile 5G Box IDUgeneric	>=0 <1.1.0.651412	1.1.0.651412

Recommended response

Check inventory. Check lockfiles and deployed manifests for WNC/T-Mobile 5G Box IDU.
Review the reported fix. Update WNC/T-Mobile 5G Box IDU to 1.1.0.651412 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Sep 16, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 16, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Sep 16, 2026

Sources and claim methodology

Source referencecert.pl

Upstream source 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

Quoted source text, attributed separately from HOL analysis.