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CVE-2026-40407· NVD / CVE Program· CNA microsoft

Windows Common Log File System Driver Elevation of Privilege Vulnerability

Heap-based buffer overflow in Windows Common Log File System Driver allows an authorized attacker to elevate privileges locally.

HighCVSS 7.8 · v3.1—No exploit No fix recorded
Published
May 12, 2026
Updated
Aug 10, 2026
EPSS
0.3% · 24th percentile
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JSON

Action score

31

Monitor

Low priority for now.

CVSS
31 / 40 · 7.8 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.3%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
total

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · microsoft
7.8
NVD has not scored this yet; the score shown is the CNA’s.

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Affected systems

VendorProduct
microsoftwindows 10 1607
microsoftwindows 10 1809
microsoftwindows 10 21h2
microsoftwindows 10 22h2
microsoftwindows 11 23h2
microsoftwindows 11 24h2
microsoftwindows 11 25h2
microsoftwindows 11 26h1
microsoftwindows server 2012
microsoftwindows server 2016
microsoftwindows server 2019
microsoftwindows server 2022

and 2 more

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • microsoft windows server 2012all versions
  • microsoft windows server 2012r2
  • microsoft windows server 2016before 10.0.14393.9140
  • microsoft windows server 2019before 10.0.17763.8755
  • microsoft windows server 2022before 10.0.20348.5074
  • microsoft windows server 2022 23h2before 10.0.25398.2330
  • microsoft windows server 2025before 10.0.26100.32772

Versions reported by the vendor

Affected version ranges reported by the assigning authority (microsoft). Independent of NVD's CPE analysis and usually ahead of it.

  • Microsoft Windows 10 Version 1607

    • 10.0.14393.0 and later · before 10.0.14393.9140affected

  • Microsoft Windows 10 Version 1809

    • 10.0.17763.0 and later · before 10.0.17763.8755affected

  • Microsoft Windows 10 Version 21H2

    • 10.0.19044.0 and later · before 10.0.19044.7291affected

  • Microsoft Windows 10 Version 22H2

    • 10.0.19045.0 and later · before 10.0.19045.7417affected

  • Microsoft Windows 11 version 23H2

    • 10.0.22631.0 and later · before 10.0.22631.7079affected

  • Microsoft Windows 11 Version 23H2

    • 10.0.22631.0 and later · before 10.0.22631.7219affected

  • Microsoft Windows 11 Version 24H2

    • 10.0.26100.0 and later · before 10.0.26100.8457affected

  • Microsoft Windows 11 Version 25H2

    • 10.0.26200.0 and later · before 10.0.26200.8457affected

  • Microsoft Windows 11 version 26H1

    • 10.0.28000.0 and later · before 10.0.28000.2113affected

  • Microsoft Windows Server 2012

    • 6.2.9200.0 and later · before 6.2.9200.26079affected

  • Microsoft Windows Server 2012 (Server Core installation)

    • 6.2.9200.0 and later · before 6.2.9200.26079affected

  • Microsoft Windows Server 2012 R2

    • 6.3.9600.0 and later · before 6.3.9600.23181affected

Same product

microsoft: all records

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Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

No fix version is recorded for this entry. Check the references for vendor advisories.

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

  • CVE-2026-85880119 days apartWindows Advanced Local Procedure Call (ALPC) Elevation of Privilege VulnerabilityKEV
    62This week
  • CVE-2025-21418455 days apartWindows Ancillary Function Driver for WinSock Elevation of Privilege VulnerabilityKEV
    61This week
  • CVE-2026-4729128 days apartHTTP.sys Remote Code Execution Vulnerability
    39Monitor
  • CVE-2026-4917263 days apartWindows FTP Service Remote Code Execution Vulnerability
    39Monitor
  • CVE-2026-5033063 days apartWindows Remote Desktop Client Elevation of Privilege Vulnerability
    39Monitor
  • CVE-2026-5044763 days apartWindows Message Queuing Service (MSMQ) Remote Code Execution Vulnerability
    39Monitor

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Someone with local access to the system can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
high · data can be read
Integrity
high · data or configuration can be modified
Availability
high · the service can be disrupted
Attack vector
Local
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
High
Integrity impact
High
Availability impact
High

Weakness class (CWE)

CWE-122 · Heap-based Buffer Overflow

CVSS vector

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

nvd-secondary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

—

Noroxi analysis

No Noroxi analysis for this record yet

We don't hand-write analysis for all 385,000+ vulnerabilities; that wouldn't be honest. For notable, high-impact vulnerabilities our team writes the mechanism, detection and remediation steps.

We use this product, ask for help

Change log

No changes recorded on tracked fields yet. Score, KEV, exploit maturity and fix status changes appear here.

References

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records