# CVE-2026-40855: Command Injection in T-Mobile 5G Box IDU router via ping functionality

> An authenticated attacker can execute arbitrary commands and gain root access via the ping functionality in the T-Mobile 5G Box IDU router.

- **Severity:** Critical 9.3 (`CVSS:4.0/AV:A/AC:L/AT:N/PR:H/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 16 Sep 2026
- **Updated:** 16 Sep 2026
- **Also known as:** GHSA-5qwp-rxmm-2vwh

## What is CVE-2026-40855?

CVE-2026-40855 is a critical command injection vulnerability in WNC T-Mobile 5G Box IDU, published on 16 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

WNC T-Mobile 5G Box IDU router is vulnerable to a command injection. The vulnerability exists in the ping functionality within the /cgi-bin/portal.cgi endpoint, specifically affecting the ping_ip, ping_size, and ping_times POST parameters. The root cause is the failure to verify and sanitize user-supplied input before incorporating it into a system command. This allows an authenticated attacker to execute arbitrary commands on the shell and gain root access to the system.This issue has been fixed in firmware version 1.1.0.651412

Weakness: CWE-78 (Improper Neutralization of Special Elements used in an OS Command)

## Which versions are affected by CVE-2026-40855?


## How do I fix CVE-2026-40855?

No fix has been published for CVE-2026-40855 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-40855 being exploited?

There is no known exploitation of CVE-2026-40855 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-40855 and fix it if it is affected.

What it is: CVE-2026-40855 is a critical command injection vulnerability in WNC T-Mobile 5G Box IDU, published on 16 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-40855 in the wild and no public exploit code.

Affected product: WNC T-Mobile 5G Box IDU. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-40855/ (Markdown: https://insights.sbomify.com/CVE-2026-40855/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-40855
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-40855
- OSV: https://osv.dev/vulnerability/CVE-2026-40855

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-40855/
Summaries are generated and may contain mistakes; the official description above is the record.