# CVE-2021-46394: Memory corruption in n/a

> A stack buffer overflow in the Tenda AX3 router allows remote attackers to execute arbitrary code via a crafted HTTP 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:** 4 Mar 2022
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-qgw7-h965-2gp6

## What is CVE-2021-46394?

CVE-2021-46394 is a critical memory corruption vulnerability in Tenda Ax3 Firmware, published on 4 Mar 2022. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

There is a stack buffer overflow vulnerability in the formSetPPTPServer function of Tenda-AX3 router V16.03.12.10_CN. The v13 variable is directly retrieved from the http request parameter startIp. Then v13 will be splice to stack by function sscanf without any security check, which causes stack overflow. By POSTing the page /goform/SetPptpServerCfg with proper startIp, the attacker can easily perform remote code execution with carefully crafted overflow data.

Weakness: CWE-787 (Out-of-bounds Write)

## Which versions are affected by CVE-2021-46394?

It affects 1 product.


Products: Tenda Ax3 Firmware.

## How do I fix CVE-2021-46394?

No fix has been published for CVE-2021-46394 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-46394 being exploited?

There is no known exploitation of CVE-2021-46394 in the wild and no public exploit code.

## Other vulnerabilities in Tenda Ax3 Firmware

- [CVE-2025-69764](https://insights.sbomify.com/CVE-2025-69764/): Memory corruption in n/a (critical 9.8)
- [CVE-2025-69762](https://insights.sbomify.com/CVE-2025-69762/): Memory corruption in n/a (critical 9.8)
- [CVE-2025-69763](https://insights.sbomify.com/CVE-2025-69763/): Memory corruption in n/a (critical 9.8)
- [CVE-2025-69766](https://insights.sbomify.com/CVE-2025-69766/): Memory corruption in n/a (critical 9.8)
- [CVE-2025-55603](https://insights.sbomify.com/CVE-2025-55603/): Memory corruption in n/a (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-46394 and fix it if it is affected.

What it is: CVE-2021-46394 is a critical memory corruption vulnerability in Tenda Ax3 Firmware, published on 4 Mar 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-2021-46394 in the wild and no public exploit code.

Affected product: Tenda Ax3 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-2021-46394/ (Markdown: https://insights.sbomify.com/CVE-2021-46394/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-46394
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-46394
- OSV: https://osv.dev/vulnerability/CVE-2021-46394

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-46394/
Summaries are generated and may contain mistakes; the official description above is the record.