CVE-2026-40856: Config disclosure in T-Mobile 5G Box IDU routers

Severity: high (CVSS 7.1 v4.0)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-09-16 · updated 2026-09-28
Weakness: CWE-306

Description

WNC T-Mobile 5G Box IDU router is vulnerable to improper access control. The vulnerability exists in the wnc_maccheck.cgi endpoint, which is accessible without authentication. It allows a remote attacker to retrieve sensitive configuration data, including the administrator web password, WiFi passphrase, and technical device information.This issue has been fixed in firmware version 1.1.0.651412

Affected products

WNC T-Mobile 5G Box IDU: before 1.1.0.651412 — fixed in 1.1.0.651412

How to fix

Upgrade to a fixed version: WNC T-Mobile 5G Box IDU 1.1.0.651412. Check the vendor advisory for mitigations.

References

https://cert.pl/posts/2026/09/CVE-2026-40854

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