# CVE-2026-1638: Tenda AC21 mDMZSetCfg command injection

> Remote attackers can execute arbitrary commands on Tenda AC21 routers via the mDMZSetCfg interface, requiring immediate attention from network administrators.

- **Severity:** Medium 5.3 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:P`)
- **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:** 29 Jan 2026
- **Updated:** 23 Feb 2026
- **Also known as:** GHSA-2wx5-jfx2-287m

## What is CVE-2026-1638?

CVE-2026-1638 is a medium-severity command injection vulnerability in Tenda AC21, published on 29 Jan 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

A security flaw has been discovered in Tenda AC21 1.1.1.1/1.dmzip/16.03.08.16. The impacted element is the function mDMZSetCfg of the file /goform/mDMZSetCfg. The manipulation of the argument dmzIp results in command injection. The attack can be executed remotely. The exploit has been released to the public and may be used for attacks.

Weakness: CWE-77 (Improper Neutralization of Special Elements used in a Command), CWE-74 (Improper Neutralization of Special Elements in Output Used by a Downstream Component)

## Which versions are affected by CVE-2026-1638?

It affects 1 product.


Products: Tenda Ac21 Firmware.

## How do I fix CVE-2026-1638?

No fix has been published for CVE-2026-1638 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-1638 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-1638 exists.

## Other vulnerabilities in Tenda AC21

- [CVE-2025-9605](https://insights.sbomify.com/CVE-2025-9605/): Tenda AC21/AC23 GetParentControlInfo stack-based overflow (critical 9.3)
- [CVE-2023-24333](https://insights.sbomify.com/CVE-2023-24333/): Command injection in n/a (high 8.8)
- [CVE-2026-4565](https://insights.sbomify.com/CVE-2026-4565/): Tenda AC21 SetNetControlList formSetQosBand buffer overflow (high 8.7)
- [CVE-2026-1637](https://insights.sbomify.com/CVE-2026-1637/): Tenda AC21 AdvSetMacMtuWan fromAdvSetMacMtuWan stack-based overflow (high 8.7)
- [CVE-2025-13445](https://insights.sbomify.com/CVE-2025-13445/): Tenda AC21 SetIpMacBind stack-based overflow (high 8.7)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-1638 and fix it if it is affected.

What it is: CVE-2026-1638 is a medium-severity command injection vulnerability in Tenda AC21, published on 29 Jan 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-2026-1638 exists.

Affected product: Tenda AC21. 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-2026-1638/ (Markdown: https://insights.sbomify.com/CVE-2026-1638/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-1638
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-1638
- OSV: https://osv.dev/vulnerability/CVE-2026-1638

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-1638/
Summaries are generated and may contain mistakes; the official description above is the record.