Exploited CVEs / SonicWall / CVE-2020-5135

CVE-2020-5135

SonicWall SonicOS 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 2022-04-05 (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 v3 base
27%
EPSS exploit probability
Critical
Severity
2022-03-15
Added to KEV
2022-04-05 (past due)
CISA due date

Actively exploited SonicWall SonicOS vulnerability, Critical severity, CVSS v3 9.8. Added to the CISA KEV catalog 2022-03-15.

Senserva AI read on CVE-2020-5135CISA required actionOfficial fix for CVE-2020-5135Admin questions

Senserva AI Opinion for CVE-2020-5135

A malicious request to a SonicWall firewall running vulnerable SonicOS triggers this buffer overflow, causing denial of service and potentially arbitrary code execution. CISA confirmed exploitation in March 2022, and the flaw is Critical at CVSS 9.8. Firewalls fail loudly when crashed and silently when hijacked; both outcomes start with the same unpatched firmware.

Do this: Confirm every SonicWall firewall runs SonicOS firmware patched for CVE-2020-5135.

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

Senserva AI Opinion and rich prompt for CVE-2020-5135

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

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 September 3, 2026. Data refreshed on every build from MSRC, CISA KEV, and FIRST EPSS.

Full tracking and change history for CVE-2020-5135

Published
2022-03-15
Last revised
2022-03-15
Changes tracked
2

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

CVE-2020-5135's confirmed link to ransomware activity on 2026-08-21 is the strongest signal, briefly accompanied by a Severity dip before returning to 9.8. EPSS climbed from 26.9% to 24.6% by 2026-07-24, then back to 26.9% by 2026-08-24, showing renewed exploitation interest. Treat this as an active, high-severity threat requiring immediate remediation today.

0%25%50%75%100%CISA KEVCISA KEV on 2022-03-15RansomwareRansomware on 2026-08-212026-07-17: EPSS 27%2026-07-24: EPSS 25%2026-08-21: EPSS 25%2026-08-24: EPSS 27%EPSS 27%2022-03-152026-08-24

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

  • 2022-03-15 added to the CISA KEV catalog by CISA
  • 2026-07-17 CVSS 0.0 to 9.8; EPSS first scored at 26.9%
  • 2026-07-24 EPSS 26.9% to 24.6%
  • 2026-08-21 CVSS 9.8 to 0.0; linked to ransomware activity; CVSS 0.0 to 9.8
  • 2026-08-24 EPSS 24.6% to 26.9%

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: 2022-04-05 (past due).

Apply updates per vendor instructions.

Official fix for CVE-2020-5135

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

SonicWall PSIRT AdvisoriesCISA KEV entry

Common questions about CVE-2020-5135

Is CVE-2020-5135 actively exploited?

Yes. CVE-2020-5135 was added to the CISA Known Exploited Vulnerabilities (KEV) catalog on 2022-03-15, which means exploitation in the wild has been confirmed, not predicted. Its EPSS 30-day exploitation probability is 27%. CISA also reports it is known to be used in ransomware campaigns.

What is the CISA deadline and required action for CVE-2020-5135?

CISA set the federal (BOD 22-01) remediation due date at 2022-04-05, which has passed; treat any unremediated system as overdue. The verbatim required action: Apply updates per vendor instructions.

What fixes CVE-2020-5135?

The authoritative fix is in the vendor advisory: see SonicWall PSIRT Advisories for the patched SonicOS 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-2020-5135?

Yes. This page includes a free, ready-to-paste AI prompt containing CVE-2020-5135'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 once a day (early morning US Central).

Scope and sources

More exploited SonicWall CVEs
CVE-2026-83549CVE-2026-83548CVE-2026-15409CVE-2026-15410CVE-2025-40602CVE-2023-44221CVE-2021-20035CVE-2024-53704

All SonicWall exploited CVEs on one page: SonicWall vulnerabilities actively exploited.

Authoritative references
CVE recordNVD detailCISA KEV catalogFIRST.org EPSS

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

New to a term on this page? CVE, KB, KEV, CVSS, and EPSS are each explained once, on the Senserva security lexicon. Reference: Microsoft CVE and vulnerability management and the Microsoft patching guide.
Provided as is, without warranty; verify against the vendor advisory before acting. Data notice and terms.