# CVE-2021-40546: Denial of service in n/a

> An authenticated administrator can crash the Tenda AC6 router by sending a long string to the 5G WiFi password parameter.

- **Severity:** Medium 4.9 (`CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 5 Sep 2023
- **Updated:** 1 Oct 2024
- **Also known as:** GHSA-mf93-hqq3-h8xg

## What is CVE-2021-40546?

CVE-2021-40546 is a medium-severity denial of service vulnerability in Tenda Ac6 Firmware, published on 5 Sep 2023. An attacker needs administrator access to exploit it, with no action from the victim.

### Official description

Tenda AC6 US_AC6V4.0RTL_V02.03.01.26_cn.bin allows attackers (who have the administrator password) to cause a denial of service (device crash) via a long string in the wifiPwd_5G parameter to /goform/setWifi.

Weakness: CWE-404 (Improper Resource Shutdown or Release)

## Which versions are affected by CVE-2021-40546?

It affects 1 product.


Products: Tenda Ac6 Firmware.

## How do I fix CVE-2021-40546?

No fix has been published for CVE-2021-40546 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-40546 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2021-40546 exists.

## Other vulnerabilities in Tenda Ac6 Firmware

- [CVE-2025-27129](https://insights.sbomify.com/CVE-2025-27129/): Auth bypass in AC6 V5.0 (critical 9.8)
- [CVE-2025-29029](https://insights.sbomify.com/CVE-2025-29029/): Memory corruption in n/a (critical 9.8)
- [CVE-2025-29030](https://insights.sbomify.com/CVE-2025-29030/): Memory corruption in n/a (critical 9.8)
- [CVE-2025-29031](https://insights.sbomify.com/CVE-2025-29031/): Memory corruption in n/a (critical 9.8)
- [CVE-2025-25343](https://insights.sbomify.com/CVE-2025-25343/): Memory corruption in n/a (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-40546 and fix it if it is affected.

What it is: CVE-2021-40546 is a medium-severity denial of service vulnerability in Tenda Ac6 Firmware, published on 5 Sep 2023. An attacker needs administrator access to exploit it, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2021-40546 exists.

Affected product: Tenda Ac6 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-2021-40546/ (Markdown: https://insights.sbomify.com/CVE-2021-40546/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-40546
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-40546
- OSV: https://osv.dev/vulnerability/CVE-2021-40546

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-40546/
Summaries are generated and may contain mistakes; the official description above is the record.