# CVE-2021-20038: SonicWall SMA 100 Appliances Stack-Based Buffer Overflow

> Remote unauthenticated attackers can execute arbitrary code via a stack-based buffer overflow in the Apache httpd mod_cgi module.

- **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:** Yes, since 28 Jan 2022 (CISA KEV), used in ransomware
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 8 Dec 2021
- **Updated:** 21 Oct 2025
- **Also known as:** GHSA-jmhc-vxg9-h2g4

## What is CVE-2021-20038?

CVE-2021-20038 is a critical memory corruption vulnerability in SonicWall SMA100, published on 8 Dec 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A Stack-based buffer overflow vulnerability in SMA100 Apache httpd server's mod_cgi module environment variables allows a remote unauthenticated attacker to potentially execute code as a 'nobody' user in the appliance. This vulnerability affected SMA 200, 210, 400, 410 and 500v appliances firmware 10.2.0.8-37sv, 10.2.1.1-19sv, 10.2.1.2-24sv and earlier versions.

Weakness: CWE-787 (Out-of-bounds Write), CWE-121 (Stack-based Buffer Overflow)

## Which versions are affected by CVE-2021-20038?

It affects 5 products.


Products: Sonicwall Sma 200 Firmware, Sonicwall Sma 210 Firmware, Sonicwall Sma 400 Firmware, Sonicwall Sma 410 Firmware, Sonicwall Sma 500v Firmware.

## How do I fix CVE-2021-20038?

No fix has been published for CVE-2021-20038 yet. Limit exposure of the affected software until one is available. US federal agencies must fix it by 11 Feb 2022.

## Is CVE-2021-20038 being exploited?

Yes. Attackers have exploited CVE-2021-20038 in the wild since at least 28 Jan 2022, including in ransomware campaigns.

Public exploit code:

- SonicWall SMA-100 Unauth RCE Exploit (CVE-2021-20038) (github_poc): https://github.com/jbaines-r7/badblood
- https://github.com/vesperp/CVE-2021-20038-SonicWall-RCE (github_poc): https://github.com/vesperp/CVE-2021-20038-SonicWall-RCE
- SonicWall security audit toolkit with vulnerable CTF lab (CVE-2021-20038, CVE-2024-53704) (github_poc): https://github.com/anir0y/sonicwall-audit-toolkit
- SonicWall SMA100 Stack - Buffer Overflow/Remote Code Execution (nuclei): http/cves/2021/CVE-2021-20038.yaml

## Other vulnerabilities in SonicWall SMA100

- [CVE-2023-44221](https://insights.sbomify.com/CVE-2023-44221/): SonicWall SMA100 Appliances OS Command Injection (high 7.2, exploited in the wild)
- [CVE-2021-20035](https://insights.sbomify.com/CVE-2021-20035/): SonicWall SMA100 Appliances OS Command Injection (medium 6.5, exploited in the wild)
- [CVE-2022-22273](https://insights.sbomify.com/CVE-2022-22273/): Command injection in SonicWall SRA/SMA100 (critical 9.8)
- [CVE-2021-20042](https://insights.sbomify.com/CVE-2021-20042/): Server-side request forgery in SonicWall SMA100 (critical 9.8)
- [CVE-2021-20045](https://insights.sbomify.com/CVE-2021-20045/): Memory corruption in SonicWall SMA100 (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-20038 and fix it if it is affected.

What it is: CVE-2021-20038 is a critical memory corruption vulnerability in SonicWall SMA100, published on 8 Dec 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: Yes. Attackers have exploited CVE-2021-20038 in the wild since at least 28 Jan 2022, including in ransomware campaigns.

Affected product: SonicWall SMA100. 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-2021-20038/ (Markdown: https://insights.sbomify.com/CVE-2021-20038/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-20038
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-20038
- OSV: https://osv.dev/vulnerability/CVE-2021-20038

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-20038/
Summaries are generated and may contain mistakes; the official description above is the record.