CVE-2021-36955

Windows Common Log File System Driver Elevation of Privilege Vulnerability

HIGH

7.8

CVSS Score

Published: September 15, 2021 at 11:23 AM UTC

Updated: August 10, 2026 at 08:38 PM UTC

17 products affected across 1 vendorWindows Server 2016Windows Server 2019Windows Server 2012

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Severity

HIGH7.8

Exploitation

CISA KEV

Exploit prediction

EPSS 4%

SSVC

Active

Actively Exploited

CISA Known Exploited Vulnerabilities (KEV) Catalog

EPSS Score4.1%

EPSS (Exploit Prediction Scoring System) estimates a 4.1% chance this CVE is exploited in the wild within the next 30 days — higher than 91% of all CVEs. It complements CVSS: a high EPSS on a mid-severity CVE can still be urgent.

Microsoft Windows Common Log File System (CLFS) driver contains an unspecified vulnerability that allows for privilege escalation.

Required Action

Apply updates per vendor instructions.

Ransomware Use

Known

Added to KEV

Nov 3, 2021

Remediation Due

Nov 17, 2021

1809 days overdue

Notes

https://nvd.nist.gov/vuln/detail/CVE-2021-36955

Description

Windows Common Log File System Driver Elevation of Privilege Vulnerability

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Windows 10 1507 · Microsoft

95%

v < 10.0.10240.1906010.0.10240.0 ≤ v < 10.0.10240.1906010.0.10240.0

Affected range stops below 10.0.10240.19060, so it looks safe — our inference, not a vendor statement

Windows 10 1607 · Microsoft

95%

v < 10.0.14393.465110.0.14393.0 ≤ v < 10.0.14393.465110.0.14393.0

Affected range stops below 10.0.14393.4651, so it looks safe — our inference, not a vendor statement

Windows 10 1809 · Microsoft

95%

v < 10.0.17763.218310.0.0 ≤ v < 10.0.17763.218310.0.0 ≤ v < 10.0.19041.123710.0.17763.0 ≤ v < 10.0.17763.218310.0.0 10.0.17763.0

Affected range stops below 10.0.17763.2183, so it looks safe — our inference, not a vendor statement

Affected range stops below 10.0.19041.1237, so it looks safe — our inference, not a vendor statement

Windows 10 1909 · Microsoft

95%

v < 10.0.18363.180110.0.0 ≤ v < 10.0.18363.180110.0.0

Affected range stops below 10.0.18363.1801, so it looks safe — our inference, not a vendor statement

Windows 10 2004 · Microsoft

95%

v < 10.0.19041.123710.0.0 ≤ v < 10.0.19041.123710.0.0

Affected range stops below 10.0.19041.1237, so it looks safe — our inference, not a vendor statement

Windows 10 20H2 · Microsoft

95%

v < 10.0.19042.123710.0.0 ≤ v < 10.0.19042.123710.0.0

Affected range stops below 10.0.19042.1237, so it looks safe — our inference, not a vendor statement

Windows 10 21H1 · Microsoft

95%

v < 10.0.19043.123710.0.0 ≤ v < 10.0.19043.123710.0.0

Affected range stops below 10.0.19043.1237, so it looks safe — our inference, not a vendor statement

Windows 7 · Microsoft

95%

6.1.0 ≤ v < 6.1.7601.257126.1.0sp1

Affected range stops below 6.1.7601.25712, so it looks safe — our inference, not a vendor statement

Windows 8-1 · Microsoft

95%

6.3.0 ≤ v < 6.3.9600.201206.3.0

Affected range stops below 6.3.9600.20120, so it looks safe — our inference, not a vendor statement

Windows Rt 8-1 · Microsoft

95%

All versions

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

Patch and advisory references

References (3)

PatchVendor Advisory

Source: [email protected]

https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-36955

Vendor AdvisoryPatch

Source: cverecord

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-36955

US Government Resource

Source: 134c704f-9b21-4f2e-91b3-4a467353bcc0

https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-36955

SSVC — Action Prioritization

SSVCActiveNot automatableTotal impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

7.8HIGHmicrosoft

Vector?

Quick Info

StatusANALYZED

CWE

NVD-CWE-noinfo

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