---
id: "CVE-2021-20038"
kind: "vulnerability"
aliases: ["CVE-2021-20038"]
title: "SonicWall SMA 100 Appliances: SonicWall SMA 100 Appliances Stack-Based Buffer Overflow Vulnerability"
severity: "critical"
cvss: 9.8
epss: 0.99912
exploited: true
status: "open"
category: "infrastructure"
products: [{"name": "SonicWall SMA 100 Appliances", "fixed": [], "affected": "", "ecosystem": "vendor"}]
ecosystems: ["vendor"]
tags: ["exploited", "infrastructure", "ransomware", "self-hosted", "sma-100", "sonicwall", "vpn"]
not_affected_if: ["unknown"]
published_at: "2021-12-08T10:15:07+00:00"
first_seen_at: "2026-10-23T19:11:53+00:00"
updated_at: "2026-10-23T21:57:35+00:00"
sources: [{"source": "kev", "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2021-20038", "first_seen_at": "2026-10-23T19:11:53+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2021-20038", "first_seen_at": "2026-10-23T19:13:44+00:00"}, {"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2021-20038", "first_seen_at": "2026-10-23T21:57:35+00:00"}]
---

# SonicWall SMA 100 Appliances: SonicWall SMA 100 Appliances Stack-Based Buffer Overflow Vulnerability

SonicWall SMA 100 series VPN/access appliances contain an unauthenticated stack-based buffer overflow. An attacker who can reach the device over the network can execute code on it.

_Summary, check and fix written by a model from the sources; labelled as such._

## Affected

- vendor:SonicWall SMA 100 Appliances affected ? fixed ?

## Fix

Apply the SonicWall update for SMA 100 appliances per vendor instructions (CISA KEV required action); the fixed firmware version is unknown from these sources.

## Timeline

- 2026-10-23T19:11:53+00:00 kev https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2021-20038
- 2026-10-23T19:13:44+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2021-20038
- 2026-10-23T21:57:35+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2021-20038

## From the sources

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.

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_