# CVE-2026-31255: Command injection in n/a

> Attackers can execute arbitrary system commands on Tenda AC18 routers via the SetSambaCfg interface due to improper handling of the guestuser parameter.

- **Severity:** Medium 5.4 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 27 Apr 2026
- **Updated:** 28 Apr 2026
- **Also known as:** GHSA-9h86-xppf-f3p9

## What is CVE-2026-31255?

CVE-2026-31255 is a medium-severity command injection vulnerability in Tenda Ac18 Firmware, published on 27 Apr 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

A command injection vulnerability exists in Tenda AC18 V15.03.05.05_multi. The vulnerability is located in the /goform/SetSambaCfg interface, where improper handling of the guestuser parameter allows attackers to execute arbitrary system commands.

Weakness: CWE-77 (Improper Neutralization of Special Elements used in a Command)

## Which versions are affected by CVE-2026-31255?

It affects 1 product.


Products: Tenda Ac18 Firmware.

## How do I fix CVE-2026-31255?

No fix has been published for CVE-2026-31255 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-31255 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-31255 exists.

## Other vulnerabilities in Tenda Ac18 Firmware

- [CVE-2024-57575](https://insights.sbomify.com/CVE-2024-57575/): Memory corruption in n/a (critical 9.8)
- [CVE-2024-57579](https://insights.sbomify.com/CVE-2024-57579/): Memory corruption in n/a (critical 9.8)
- [CVE-2024-57580](https://insights.sbomify.com/CVE-2024-57580/): Memory corruption in n/a (critical 9.8)
- [CVE-2024-57581](https://insights.sbomify.com/CVE-2024-57581/): Memory corruption in n/a (critical 9.8)
- [CVE-2024-57582](https://insights.sbomify.com/CVE-2024-57582/): Memory corruption in n/a (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-31255 and fix it if it is affected.

What it is: CVE-2026-31255 is a medium-severity command injection vulnerability in Tenda Ac18 Firmware, published on 27 Apr 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-31255 exists.

Affected product: Tenda Ac18 Firmware. 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-2026-31255/ (Markdown: https://insights.sbomify.com/CVE-2026-31255/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-31255
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-31255
- OSV: https://osv.dev/vulnerability/CVE-2026-31255

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-31255/
Summaries are generated and may contain mistakes; the official description above is the record.