CVE-2026-40856
CVE-2026-40856 is a Missing Authentication vulnerability. No vendor fix is recorded yet; mitigation options are listed below.
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…
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-40856.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
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
Detection & mitigation playbook
VulnerabilityDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for the affected component, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Remediation status
No patched version of the affected component has shipped for CVE-2026-40856 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.
Mitigate without a patch
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-40856 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-40856. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-40856 in your dependencies?
O3 Security finds CVE-2026-40856 across dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.