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Actively exploitedKnown ransomware use

CVE-2020-0796 Microsoft SMBv3 Remote Code Execution Vulnerability

A remote code execution vulnerability exists in the way that the Microsoft Server Message Block 3.1.1 (SMBv3) protocol handles certain requests. An attacker who successfully exploited the vulnerability could gain the ability to execute code on the target server or client.

From the CISA KEV catalogue version 2026.11.06, with Cybergen analysis. Updated 6 Nov 2026.

Our Assessment

Should You Worry?

Patch nowCybergen assessment
  • CISA confirmed exploitation in the wild and added it to the Known Exploited Vulnerabilities catalogue on 10 Feb 2022.
  • CISA lists it as known to be used in ransomware campaigns.
  • Rated Critical severity (CVSS 10.0, scored by CISA).
  • It has been in the catalogue for 1,730 days. Systems still unpatched now have almost certainly been scanned for it.
The Vulnerability

What It Is

A remote code execution vulnerability exists in the way that the Microsoft Server Message Block 3.1.1 (SMBv3) protocol handles certain requests, aka 'Windows SMBv3 Client/Server Remote Code Execution Vulnerability'.

Affected Versions

ProductVersions
Microsoft Windows 10 Version 1903 for 32-bit Systemsunspecified
Microsoft Windows 10 Version 1903 for x64-based Systemsunspecified
Microsoft Windows 10 Version 1903 for ARM64-based Systemsunspecified
Microsoft Windows Server, version 1903 (Server Core installation)unspecified
Microsoft Windows 10 Version 1909 for 32-bit Systemsunspecified
Microsoft Windows 10 Version 1909 for x64-based Systemsunspecified

From the public CVE record, as supplied by the vendor. Always confirm against the vendor advisory.

From Watch to Action

What To Do Now

  1. 1

    Find it

    Search your asset inventory and external attack surface for Microsoft SMBv3. Include cloud images, appliances and anything a supplier runs for you.

    Attack Surface Management
  2. 2

    Fix it

    Apply updates per vendor instructions.

    Vulnerability Management
  3. 3

    Hunt for compromise

    If an affected system was reachable before you patched, assume it may have been hit. Check logs, new accounts, web shells and outbound connections from the date of exposure.

    Incident Response
  4. 4

    Prove it is fixed

    Rescan or test the system after patching. Upgrades that fail silently and forgotten secondary instances are common.

    Penetration Testing

Vendor Advisories

Regulation

The Compliance Clock

Cyber EssentialsRated critical, so if it affects devices in your Cyber Essentials scope, the update must be installed within 14 days of the vendor releasing it.NIS2If exploitation causes a significant incident, essential and important entities owe their CSIRT an early warning within 24 hours and a notification within 72 hours.DORAFinancial entities must classify ICT incidents and send an initial notification for a major incident within strict deadlines, with exploited flaws a common cause.US federal (BOD 22-01)Federal civilian agencies had until 10 Aug 2022 to remediate. A sensible benchmark for everyone else.

General guidance, not legal advice. Your obligations depend on your sector, scope and jurisdiction.

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Evidence

Sources

  1. CISA Known Exploited Vulnerabilities catalogue
  2. NVD: CVE-2020-0796
  3. CVE record: CVE-2020-0796
  4. FIRST EPSS
  5. portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2020-0796
  6. packetstormsecurity.com/files/156731/CoronaBlue-SMBGhost-Microsoft-Windows-10-SMB-3.1.1-Proof-Of-Con
  7. packetstormsecurity.com/files/156732/Microsoft-Windows-SMB-3.1.1-Remote-Code-Execution.html
  8. packetstormsecurity.com/files/156980/Microsoft-Windows-10-SMB-3.1.1-Local-Privilege-Escalation.html
  9. packetstormsecurity.com/files/157110/SMBv3-Compression-Buffer-Overflow.html
  10. packetstormsecurity.com/files/157901/Microsoft-Windows-SMBGhost-Remote-Code-Execution.html
  11. packetstormsecurity.com/files/158054/SMBleed-SMBGhost-Pre-Authentication-Remote-Code-Execution-Proof