# CVE-2020-26728: Command injection in n/a

> Remote attackers can execute arbitrary code on Tenda AC9 routers by injecting shell metacharacters into the guestuser field via a POST request.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 11 Feb 2022
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-586v-26wc-h2mw

## What is CVE-2020-26728?

CVE-2020-26728 is a critical command injection vulnerability in Tenda Ac9 Firmware, published on 11 Feb 2022. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A vulnerability was discovered in Tenda AC9 v3.0 V15.03.06.42_multi and Tenda AC9 V1.0 V15.03.05.19(6318)_CN which allows for remote code execution via shell metacharacters in the guestuser field to the __fastcall function with a POST request.

## Which versions are affected by CVE-2020-26728?

It affects 1 product.


Products: Tenda Ac9 Firmware.

## How do I fix CVE-2020-26728?

No fix has been published for CVE-2020-26728 yet. Limit exposure of the affected software until one is available.

## Is CVE-2020-26728 being exploited?

There is no known exploitation of CVE-2020-26728 in the wild and no public exploit code.

## Other vulnerabilities in Tenda Ac9 Firmware

- [CVE-2025-45042](https://insights.sbomify.com/CVE-2025-45042/): Command injection in n/a (critical 9.8)
- [CVE-2025-44872](https://insights.sbomify.com/CVE-2025-44872/): Command injection in n/a (critical 9.8)
- [CVE-2025-44877](https://insights.sbomify.com/CVE-2025-44877/): Command injection in n/a (critical 9.8)
- [CVE-2025-45427](https://insights.sbomify.com/CVE-2025-45427/): Memory corruption in n/a (critical 9.8)
- [CVE-2025-45428](https://insights.sbomify.com/CVE-2025-45428/): Memory corruption in n/a (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-26728 and fix it if it is affected.

What it is: CVE-2020-26728 is a critical command injection vulnerability in Tenda Ac9 Firmware, published on 11 Feb 2022. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2020-26728 in the wild and no public exploit code.

Affected product: Tenda Ac9 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-2020-26728/ (Markdown: https://insights.sbomify.com/CVE-2020-26728/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-26728
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-26728
- OSV: https://osv.dev/vulnerability/CVE-2020-26728

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-26728/
Summaries are generated and may contain mistakes; the official description above is the record.