CVE-2026-56649
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 · uneditedConcurrent execution using shared resource with improper synchronization ('race condition') in Windows Network File System allows an unauthorized attacker to execute code over a network.
In the news
Third-party coverage- Microsoft July 2026 Patch Tuesday fixes massive 570 flaws, 3 zero-days
- Microsoft CVE Summary - Bleeping Computer
Surfaced from public web coverage — external links open in a new tab.
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 · moderate confidenceA race condition vulnerability exists in Windows Network File System where improper synchronization of shared resources during concurrent operations allows an unauthenticated attacker to execute arbitrary code remotely over the network.
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< 10.0.14393.9339< 10.0.17763.9020< 10.0.19044.7548< 10.0.19045.7548< 10.0.26100.8875< 10.0.26200.8875< 10.0.28000.2269all versions= r2CVSS 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
- High
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/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 checksWork through these to decide whether this CVE applies to you.
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Verify NFS server role is installedOpen PowerShell and run: Get-WindowsFeature -Name *NFS* | Select-Object Name, InstallStateAffected if InstallState shows 'Installed' or 'Available' - the NFS role is present on the system
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Confirm NFS service is runningOpen Services console (services.msc) or run: Get-Service -Name NfsService | Select-Object Status, StartTypeAffected if Status shows 'Running' - the NFS service is actively running and vulnerable to network exploitation
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Check Windows version against affected rangesRun: winver; or in PowerShell: [System.Environment]::OSVersion.VersionStringAffected if Version is below 10.0.14393.9339 (Win10 1607), below 10.0.17763.9020 (Win10 1809), below 10.0.19044.7548 (Win10 21h2), below 10.0.19045.7548 (Win10 22h2), below 10.0.26100.8875 (Win11 24h2), below 10.0.26200.8875 (Win11 25h2), or below 10.0.28000.2269 (Win11 26h1), or is Windows Server 2012/2012 R2
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Verify NFS ports are listening and exposedRun: netstat -ano | findstr :2049 ; or: Get-NetTCPConnection -LocalPort 2049Affected if Port 2049 (NFS) is listening and bound to an external-facing adapter - the vulnerability is network-exploitable
System is affected if NFS server role is installed and running on a Windows version within the affected ranges, with port 2049 exposed to untrusted network segments.
Generated from the published advisory. Verify against your own configuration.
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 · scoped10.0.14393.933910.0.17763.902010.0.19044.7548
Apply Microsoft security updates for Windows NFS when released; temporarily restrict NFS access to trusted IP ranges and implement network segmentation to limit exposure.
Windows 10 1607: build 10.0.14393.9339 or later | Windows 10 1809: build 10.0.17763.9020 or later | Windows 10 21h2: build 10.0.19044.7548 or later | Windows 10 22h2: build 10.0.19045.7548 or later | Windows 11 24h2: build 10.0.26100.8875 or later | Windows 11 25h2: build 10.0.26200.8875 or later |
- 1. Identify the current Windows version by running 'winver' or checking System Properties
- 2. Determine if the system is running an affected version based on the build number
- 3. For Windows 10 systems: Navigate to Settings > Update & Security > Windows Update and check for updates
- 4. Apply the cumulative update that includes the fix for CVE-2026-56649
- 5. For Windows 11 systems: Use Windows Update or download the specific cumulative update from the Microsoft Update Catalog
- 6. For Windows Server 2012/R2: This version is listed as 'all versions' affected - Microsoft may not be providing security updates for Windows Server 2012; consider migrating to a supported Windows Server version
- 7. After applying updates, verify the build number matches or exceeds the fixed version for your Windows release
- 8. Restart the system if prompted to complete the update installation
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation4.0 h
- Implementation8.0 h
- Testing6.0 h
- Review / QA3.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $5,888.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-56649 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-56649 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
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