CVE-2026-50407
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 · uneditedHeap-based buffer overflow in Windows Resilient File System (ReFS) allows an authorized attacker to elevate privileges locally.
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 confidenceHeap-based buffer overflow vulnerability in Windows Resilient File System (ReFS) allows a locally authorized attacker to execute code with elevated privileges by overflowing a heap allocation in the ReFS driver.
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< 10.0.28000.2525< 10.0.14393.9339CVSS 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
- Local
- Complexity
- Low
- Privileges
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:L/AC:L/PR:L/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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Check Windows version build numberRun 'winver' or 'systeminfo' from command prompt, or query registry key HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion and locate the 'Build' value (for example, 14393, 17763, 19044, etc.)Affected if The build number falls below any of these thresholds: 14393.9339 (Windows 10 1607/Server 2016), 17763.9020 (Windows 10 1809), 19044.7548 (Windows 10 21h2), 19045.7548 (Windows 10 22h2), 26100.8875 (Windows 11 24h2), 26200.8875 (Windows 11 25h2), or 28000.2525 (Windows 11 26h1)
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Identify ReFS-formatted volumesOpen DiskPart (type 'diskpart' from command prompt), then run 'list volume' to see all volumes, followed by 'select volume X' and 'detail volume' to check if the File System column shows 'ReFS'Affected if Any volume displays 'ReFS' as the file system, indicating ReFS is in use on this system
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Verify ReFS driver presenceCheck if refs.sys exists in the C:\Windows\System32\drivers\ directory, or query the driver loaded status via 'sc query refs' or 'driverquery /v | findstr refs'Affected if The refs.sys driver file exists on the system or is listed as a loaded driver (even if no ReFS volumes are actively mounted, the driver could potentially be triggered)
A system is affected if it runs a Windows version with a build number below the thresholds listed AND has the ReFS driver present (whether or not ReFS volumes are actively mounted).
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.
From vendor data10.0.14393.933910.0.17763.902010.0.19044.7548
Apply Microsoft security patches for ReFS when released; prioritize patching systems with untrusted local users; consider disabling ReFS if not required in environments with high security sensitivity.
- Consultation2.0 h
- Implementation1.0 h
- Testing4.0 h
- Review / QA2.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-50407 — 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-2026-50407 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
- No weaponised exploit code, or anything meant to cause harm
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