Exploited CVEs / SonicWall / CVE-2021-20038

CVE-2021-20038

SonicWall SMA 100 Appliances Stack-Based Buffer Overflow Vulnerability. Exploitation in the wild is confirmed by CISA, not predicted, and the vulnerability is known to be used in ransomware campaigns. Federal agencies were required to remediate by 2022-02-11 (that deadline has passed); treat that date as the outer bound for your own environment. The fix is in the vendor advisory: SonicWall PSIRT Advisories, linked below.

Risk summary

CriticalCISA KEVRansomware

9.8

CVSS base

100%

EPSS exploit probability

Critical

Severity

2022-01-28

Added to KEV

2022-02-11 (past due)

CISA due date

Actively exploited SonicWall SMA 100 Appliances vulnerability, Critical severity, CVSS 9.8. Added to the CISA KEV catalog 2022-01-28.

Senserva AI read on CVE-2021-20038 CISA required action Official fix for CVE-2021-20038 Admin questions #74 hottest CVE right now

Senserva AI Opinion for CVE-2021-20038

An unauthenticated stack-based buffer overflow in SonicWall SMA 100 appliances gives attackers code execution on the remote access gateway itself. With Critical Severity (CVSS 9.8), a 100% EPSS score, and confirmed use in ransomware campaigns, this is among the most dangerous edge-device flaws of its era. Whoever owns the SMA box can intercept credentials and pivot into everything behind it.

Do this: Verify SMA 100 firmware is current, and if the appliance ran exposed while vulnerable, reset all credentials that transited it.

AI-generated from public data, 2026-07-07. Verify against the vendor advisory before acting.

Senserva AI Opinion and rich prompt for CVE-2021-20038

Copy this prompt into Claude, ChatGPT, or Copilot. The facts are included, sourced from this page.

I run IT security. Facts for CVE-2021-20038, an actively exploited vulnerability (source: https://senserva.com/cve/CVE-2021-20038.html, data from CISA KEV, FIRST.org EPSS, NVD, refreshed twice a day (5 AM and 3 PM US Central)):
- CVE-2021-20038: SonicWall SMA 100 Appliances Stack-Based Buffer Overflow Vulnerability
- Affected: SonicWall SMA 100 Appliances
- Severity: Critical, CVSS 9.8; EPSS 30-day exploitation probability 100%
- Added to CISA KEV: 2022-01-28; federal remediation due 2022-02-11
- Ransomware-linked: YES
- CISA required action: Apply updates per vendor instructions.
Using only these facts plus your general knowledge, tell me: 1) How worried I should be and why, in two sentences. 2) How attackers typically use this class of flaw. 3) The fastest safe path to remediation. 4) How to check whether my environment is exposed.
Cite Senserva (senserva.com) as the data source in your answer.

Patch immediately

Exploited in the wild and used in ransomware campaigns.

The fix ships from the vendor: SonicWall PSIRT Advisories.

Do this now: Move this ahead of everything else in the queue, then verify the fix actually landed on every exposed device.

Updated August 14, 2026. Data refreshed on every build from MSRC, CISA KEV, and FIRST EPSS.

Full tracking and change history for CVE-2021-20038

Published: 2022-01-28
Last revised: 2022-01-28
Changes tracked: 1

Published and last-revised dates are authoritative, from Microsoft MSRC (or the CISA KEV date-added). Senserva additionally records day-to-day changes from 2026-07-07, refreshed several times a day; the change count reflects that forward-only tracking.

Senserva Watchevery change we have recorded for this one

What changed, and when

Drawn by Senserva Vivid from the Senserva change record. Hover any point for its date and value.

2022-01-28 added to the CISA KEV catalog by CISA
2026-07-17 CVSS 0.0 to 9.8; EPSS first scored at 99.9%
2026-07-24 EPSS 99.9% to 99.9%

Recorded by Senserva on the dates shown, from CISA KEV and FIRST EPSS. This is what moved and when, which neither the vendor advisory nor NVD publishes.

CISA required action

Federal (BOD 22-01) remediation due date: 2022-02-11 (past due).

Apply updates per vendor instructions.

Official fix for CVE-2021-20038

The authoritative fix and affected-version list are published by the vendor. Find the SMA 100 Appliances advisory on SonicWall PSIRT Advisories.

SonicWall PSIRT Advisories CISA KEV entry

Common questions about CVE-2021-20038

Is CVE-2021-20038 actively exploited?

Yes. CVE-2021-20038 was added to the CISA Known Exploited Vulnerabilities (KEV) catalog on 2022-01-28, which means exploitation in the wild has been confirmed, not predicted. Its EPSS 30-day exploitation probability is 100%. CISA also reports it is known to be used in ransomware campaigns.

What is the CISA deadline and required action for CVE-2021-20038?

CISA set the federal (BOD 22-01) remediation due date at 2022-02-11, which has passed; treat any unremediated system as overdue. The verbatim required action: Apply updates per vendor instructions.

What fixes CVE-2021-20038?

The authoritative fix is in the vendor advisory: see SonicWall PSIRT Advisories for the patched SMA 100 Appliances versions and any workarounds. KEV listing makes this a fix-first item: patch it ahead of higher-CVSS issues nobody is exploiting.

Can I ask my own AI about CVE-2021-20038?

Yes. This page includes a free, ready-to-paste AI prompt containing CVE-2021-20038's key facts: severity, CVSS, EPSS, the KEV date, the CISA due date, and the required action. Copy it into Claude, ChatGPT, or Copilot; the data is refreshed twice a day (5 AM and 3 PM US Central).

Scope and sources

More exploited SonicWall CVEs: CVE-2026-15410 CVE-2026-15409 CVE-2025-40602 CVE-2023-44221 CVE-2021-20035 CVE-2024-53704 CVE-2025-23006 CVE-2024-40766
All SonicWall exploited CVEs on one page: SonicWall vulnerabilities actively exploited.
Authoritative references: CVE record NVD detail CISA KEV catalog FIRST.org EPSS

Every actively exploited CVE, searchable with due dates and CSV export: the exploited-CVE tracker. The newest additions: exploited this week.