CVE-2021-20042

What it is

An unauthenticated remote attacker can use SMA 100 as an unintended proxy or intermediary undetectable proxy to bypass firewall rules. This vulnerability affected SMA 200, 210, 400, 410 and 500v appliances.

At a glance

Exploitability

Can be exploited over the network without logging in. High risk of data exposure, data tampering, service disruption.

Exploit odds

3.7% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2021-12-08 10:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 03:33 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 3.7% in the next 30 days (EPSS).
• Severity: 9.8 CRITICAL (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2021-12-08 10:15 UTC

Last modified

2026-06-17 03:33 UTC

Exploit probability

3.7% · EPSS, next 30 days

Weakness

CWE-441

Record status

Modified

Affected

• Sonicwall Sma 200 Firmware 9.0.0.11-31sv
• Sonicwall Sma 200 Firmware 10.2.0.8-37sv
• Sonicwall Sma 200 Firmware 10.2.1.1-19sv
• Sonicwall Sma 210 Firmware 9.0.0.11-31sv
• Sonicwall Sma 210 Firmware 10.2.0.8-37sv
• Sonicwall Sma 210 Firmware 10.2.1.1-19sv
• Sonicwall Sma 410 Firmware 9.0.0.11-31sv
• Sonicwall Sma 410 Firmware 10.2.0.8-37sv

Attack profile CVSS 3.1 · 9.8

Attack vector

Network

Complexity

Low

Privileges needed

None

User interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2021-20042.md and follow it. Check whether this project is affected by CVE-2021-20042. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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