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

Exploited in the wild Critical 9.8 Published 8 Dec 2021 Updated 21 Oct 2025

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

Exploited in the wild: Since 28 Jan 2022
Login needed: Not needed
Attackable: Over the internet
Victim action needed: Not needed
Fix: None listed

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, CWE-121

Which versions are affected by CVE-2021-20038?

It affects 5 products.

Products include 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.

Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.

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: 1 Nuclei template and 3 proofs of concept on GitHub.

Sources

Also known as GHSA-jmhc-vxg9-h2g4.