# CVE-2026-31847: Hidden Functionality Enables Remote Telnet Activation via /goform/setSysTools in Nexxt Nebula 300+

> An authenticated attacker can remotely enable Telnet on the device, potentially leading to code execution and privilege escalation.

- **Severity:** High 8.5 (`CVSS:4.0/AV:A/AC:L/AT:N/PR:H/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N`)
- **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:** 23 Mar 2026
- **Updated:** 10 Aug 2026
- **Also known as:** GHSA-892q-6j8f-3q9c

## What is CVE-2026-31847?

CVE-2026-31847 is a high-severity vulnerability in Nexxt Solutions Nebula 300+, published on 23 Mar 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

Hidden functionality in the /goform/setSysTools endpoint in Nexxt Solutions Nebula 300+ firmware through version 12.01.01.37 allows remote enablement of a Telnet service. By sending a crafted POST request with parameters such as telnetManageEn=true and telnetPwd, an authenticated attacker can activate a Telnet service on port 23.

Weakness: CWE-912 (Hidden Functionality)

## Which versions are affected by CVE-2026-31847?

It affects 1 product.


Products: Nexxtsolutions Nebula300plus Firmware.

## How do I fix CVE-2026-31847?

No fix has been published for CVE-2026-31847 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-31847 being exploited?

There is no known exploitation of CVE-2026-31847 in the wild and no public exploit code.

## Other vulnerabilities in Nexxt Solutions Nebula 300+

- [CVE-2026-31848](https://insights.sbomify.com/CVE-2026-31848/): Reversible ecos_pw Cookie Allows Authentication Bypass in Nexxt Nebula 300+ (high 8.7)
- [CVE-2026-31851](https://insights.sbomify.com/CVE-2026-31851/): Nexxt Nebula 300+ - Lack of Rate Limiting Enables Brute-Force Attacks (high 7.7)
- [CVE-2026-31849](https://insights.sbomify.com/CVE-2026-31849/): Missing CSRF Protection on Administrative Endpoints in Nexxt Nebula 300+ (high 7.2)
- [CVE-2026-31850](https://insights.sbomify.com/CVE-2026-31850/): Plaintext Storage of Credentials in Configuration Backup in Nexxt Nebula 300+ (medium 6.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-31847 and fix it if it is affected.

What it is: CVE-2026-31847 is a high-severity vulnerability in Nexxt Solutions Nebula 300+, published on 23 Mar 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-2026-31847 in the wild and no public exploit code.

Affected product: Nexxt Solutions Nebula 300+. 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-2026-31847/ (Markdown: https://insights.sbomify.com/CVE-2026-31847/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-31847
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-31847
- OSV: https://osv.dev/vulnerability/CVE-2026-31847

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-31847/
Summaries are generated and may contain mistakes; the official description above is the record.