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Windows 10Operating system · Microsoft

CVE-2016-3340

HIGH · 7.8 CVSS v3.0 Published 2016-11-10
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
81/100
Remediation priority · High
No privileges

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
The Common Log File System (CLFS) driver in Microsoft Windows Vista SP2, Windows Server 2008 SP2 and R2 SP1, Windows 7 SP1, Windows 8.1, Windows Server 2012 Gold and R2, Windows RT 8.1, Windows 10 Gold, 1511, and 1607, and Windows Server 2016 allows local users to gain privileges via a crafted application, aka "Windows Common Log File System Driver Elevation of Privilege Vulnerability," a different vulnerability than CVE-2016-0026, CVE-2016-3332, CVE-2016-3333, CVE-2016-3334, CVE-2016-3335, CVE-2016-3338, CVE-2016-3342, CVE-2016-3343, and CVE-2016-7184.

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

CVE-2016-3340 is a local privilege escalation vulnerability in the Windows Common Log File System (CLFS) driver. The flaw allows a local authenticated attacker to run a specially crafted application that exploits improper handling of objects in kernel mode, enabling elevation from standard user to SYSTEM/Administrator privileges.

MitigationApply the relevant Microsoft security update (MS16-111) to patch the CLFS driver vulnerability. Prior to patching, restrict local user permissions and monitor for suspicious executables; however, patching is the definitive remediation.

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 10Operating system
Affected:all versions= 1511= 1607
Windows 7Operating system
Affected:all versions
Windows 8.1Operating system
Affected:all versions
Windows Rt 8.1Operating system
Affected:all versions
Windows Server 2008Operating system
Affected:all versions= r2
Windows Server 2012Operating system
Affected:all versions= r2
Windows Server 2016Operating system
Affected:all versions
Windows VistaOperating 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
Local
Complexity
Low
Privileges
None
User interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.0/AV:L/AC:L/PR:N/UI:R/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 checks

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

  1. Confirm Windows version is within affected range
    Run 'winver' or 'systeminfo | findstr "OS Name"' to identify the Windows edition and version
    Affected if The system runs Windows 10 (all versions, 1511, 1607), Windows 7 (all versions), Windows 8.1 (all versions), Windows RT 8.1, Windows Server 2008 (all, R2), Windows Server 2012 (all, R2), Windows Server 2016, or Windows Vista (all versions)
  2. Verify MS16-111 security update is installed
    Run 'wmic qfe list' or 'systeminfo | findstr "KB3185319"' to check if update KB3185319 is present
    Affected if The security update KB3185319 (MS16-111) is NOT installed on the system
  3. Check CLFS driver version
    Run 'driverquery /v /fo list | findstr "CLFS"' to locate the Common Log File System driver, then check the file version of C:\Windows\System32\CLFS.sys via right-click properties
    Affected if CLFS.sys version is lower than the patched version or the driver exists on an unpatched Windows installation from the affected list
  4. Confirm CLFS driver is loaded
    Run 'sc query clfs' to check if the Common Log File System service/driver is present and running
    Affected if The CLFS driver is loaded on an unpatched system (required condition for exploitation)

A system is affected if it runs any Windows version from the affected list AND lacks the MS16-111 (KB3185319) security update, allowing a local authenticated user to elevate privileges via the CLFS driver.

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.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Apply the relevant Microsoft security update (MS16-111) to patch the CLFS driver vulnerability. Prior to patching, restrict local user permissions and monitor for suspicious executables; however, patching is the definitive remediation.

Fix this in Windows 10 Scoped from the published advisory
  • Consultation3.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
12.0 hours of engineering $2,130
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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-2016-3340 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