Exploited CVEs / SonicWall / CVE-2021-20023

CVE-2021-20023

SonicWall Email Security Path Traversal 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 2021-11-17 (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

MediumCISA KEVRansomware

4.9

CVSS base

50%

EPSS exploit probability

Medium

Severity

2021-11-03

Added to KEV

2021-11-17 (past due)

CISA due date

Actively exploited SonicWall Email Security vulnerability, Medium severity, CVSS 4.9. Added to the CISA KEV catalog 2021-11-03.

Senserva AI read on CVE-2021-20023 CISA required action Official fix for CVE-2021-20023 Admin questions

Senserva AI Opinion for CVE-2021-20023

Despite a Medium Severity rating at CVSS 4.9, this SonicWall Email Security path traversal has a 51 percent EPSS score and confirmed ransomware use, because it completes an exploit chain with CVE-2021-20021 and CVE-2021-20022. It lets a post-authenticated attacker read files on the appliance, which in a chain means harvesting secrets. Scoring bugs in isolation understates chained ones, and this entry proves it.

Do this: Patch SonicWall Email Security for the entire CVE-2021-20021 through CVE-2021-20023 chain and rotate credentials stored on affected appliances.

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

Senserva AI Opinion and rich prompt for CVE-2021-20023

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

I run IT security. Facts for CVE-2021-20023, an actively exploited vulnerability (source: https://senserva.com/cve/CVE-2021-20023.html, data from CISA KEV, FIRST.org EPSS, NVD, refreshed twice a day (5 AM and 3 PM US Central)):
- CVE-2021-20023: SonicWall Email Security Path Traversal Vulnerability
- Affected: SonicWall Email Security
- Severity: Medium, CVSS 4.9; EPSS 30-day exploitation probability 50%
- Added to CISA KEV: 2021-11-03; federal remediation due 2021-11-17
- 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-2021-20023

Published: 2021-11-03
Last revised: 2021-11-03
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

2021-11-03 added to the CISA KEV catalog by CISA
2026-07-17 CVSS 0.0 to 4.9; EPSS first scored at 51.4%
2026-07-24 EPSS 51.4% to 50.2%

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: 2021-11-17 (past due).

Apply updates per vendor instructions.

Official fix for CVE-2021-20023

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

SonicWall PSIRT Advisories CISA KEV entry

Common questions about CVE-2021-20023

Is CVE-2021-20023 actively exploited?

Yes. CVE-2021-20023 was added to the CISA Known Exploited Vulnerabilities (KEV) catalog on 2021-11-03, which means exploitation in the wild has been confirmed, not predicted. Its EPSS 30-day exploitation probability is 50%. CISA also reports it is known to be used in ransomware campaigns.

What is the CISA deadline and required action for CVE-2021-20023?

CISA set the federal (BOD 22-01) remediation due date at 2021-11-17, which has passed; treat any unremediated system as overdue. The verbatim required action: Apply updates per vendor instructions.

What fixes CVE-2021-20023?

The authoritative fix is in the vendor advisory: see SonicWall PSIRT Advisories for the patched SonicWall Email Security 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-2021-20023?

Yes. This page includes a free, ready-to-paste AI prompt containing CVE-2021-20023'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.