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Actively exploited in the wild. This CVE is on the CISA Known Exploited Vulnerabilities list — treat remediation as urgent. Federal remediation due by 10 Aug 2022. Known ransomware use
Windows 10 1903Operating system · Microsoft

CVE-2020-0796

CRITICAL · 10.0 CVSS v3.1 Published 2020-03-12
Patch available
A vendor patch is available. No clean upgrade release — apply the published patch.
See remediation →
100/100
Remediation priority · Urgent
In the wild Ransomware High EPSS Public exploit Remotely reachable No privileges Zero-click Patch available

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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'.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

A critical buffer overflow vulnerability in SMBv3.1.1's handling of compressed packets allows unauthenticated remote attackers to execute arbitrary code by sending specially crafted SMB requests to affected Windows systems acting as SMB servers or clients.

MitigationApply Microsoft security updates (KB4551762 for Windows 10/Server 1903/1909) and consider disabling SMBv3 compression or blocking port 445 at network boundaries as compensating controls until patches are deployed.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Windows 10 1903Operating system
Affected:all versions
Windows 10 1909Operating system
Affected:all versions
Windows Server 1903Operating system
Affected:all versions
Windows Server 1909Operating system
Affected:all versions

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Changed
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify Windows version
    Run 'winver', 'systeminfo | findstr /B /C:"OS Name" /C:"OS Version"', or 'Get-ComputerInfo | Select-Object OsName, OsVersion'
    Affected if Version shows Windows 10 1903, Windows 10 1909, Windows Server 1903, or Windows Server 1909
  2. Confirm SMBv3 compression capability is present
    Check registry key 'HKLM:\SYSTEM\CurrentControlSet\Services\LanmanServer\Parameters' for 'DisableCompression' value (if present and set to 1, compression is disabled; if absent or 0, compression is enabled)
    Affected if DisableCompression registry value is absent or set to 0, meaning SMBv3 compression is enabled
  3. Verify SMB service is listening
    Run 'netstat -an | findstr :445' or 'Test-NetConnection -ComputerName localhost -Port 445' to check if SMB TCP port 445 is open
    Affected if Port 445 is listening and the system is reachable on that port from network attackers

Your system is affected if it runs Windows 10 1903/1909 or Windows Server 1903/1909, has SMBv3 compression enabled (DisableCompression not set to 1), and has SMB port 445 exposed to untrusted networks.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Patch available Apply the vendor patch
Vendor patch portal.msrc.microsoft.com →
Interim mitigation

Apply Microsoft security updates (KB4551762 for Windows 10/Server 1903/1909) and consider disabling SMBv3 compression or blocking port 445 at network boundaries as compensating controls until patches are deployed.

Recommended fix High confidence

Microsoft Security Update KB4551762 for Windows 10 version 1903/1909 and Windows Server version 1903/1909

  1. Apply the March 2020 security update from Microsoft for this vulnerability. For Windows 10 version 1903 and version 1909, install the cumulative security update (KB4551762). For Windows Server version 1903 and version 1909, install the corresponding security update.
  2. Verify the update was successfully installed by checking Windows Update history or by reviewing installed updates.
  3. After patching, ensure SMB compression is disabled as an additional defensive measure by setting the registry key 'HKLM\SYSTEM\CurrentControlSet\Services\LanmanServer\Parameters' with DWORD 'DisableCompression' set to 1, if recommended by Microsoft guidance.
  4. Restart the affected systems to ensure the patches take full effect.
  5. Verify the vulnerability is remediated using vulnerability scanning tools or by checking that SMB negotiation fails for vulnerable configurations.
Caveat Standard risks apply with Windows updates - test in staging environment before broad deployment; some updates may require restart

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Windows 10 1903 Exploited in the wild — priority engagement
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing2.0 h
  • Review / QA1.0 h
9.0 hours of engineering $1,600
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An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,560.

Scan for this in your stack

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2020-0796 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data