CVE-2021-43226: Microsoft Windows Privilege Escalation Vulnerability

What it is

Windows Common Log File System Driver Elevation of Privilege Vulnerability

Description quoted from the CVE record (assigned by microsoft, published 2021-12-15).

How it can be exploited

Exploitable with local access with low attack complexity needing low privileges and no user interaction. Impact: 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/E:U/RL:O/RC:C

CISA assessment (SSVC): CISA assesses exploitation as active. Automatable: no. Technical impact: total.

On CISA KEV since

2025-10-06

US federal deadline

2025-10-27

Ransomware use

Yes

Public exploit evidence (Exploit Observer)

Also known as: BDU:2022-01303, CNNVD-202112-1166, EUVD-2021-30170, GHSA-98jh-5xvm-p5ph, GHSA-w3v4-69ph-pfjp

VEDAS cluster: VEDAS:BELLAHUMMINGBIRD

Exploit Observer links 1 piece of public exploit code or detection modules that name this CVE or one of its aliases.

Exploit code and modules (1)

Code that names this CVE. A repository can be a working exploit, a scanner, a fake or malware; read it before running anything.

• Code repository: https://github.com/rosayxy/cve-2021-43226poc

Vulnerability databases and vendor advisories (8)

Catalogue entries, not exploit evidence.

• Vulnerability database or vendor advisory: https://euvd.enisa.europa.eu/enisa/EUVD-2021-30170
• Vulnerability database or vendor advisory: https://github.com/advisories/GHSA-98jh-5xvm-p5ph
• Vulnerability database or vendor advisory: https://github.com/advisories/GHSA-w3v4-69ph-pfjp
• Vulnerability database or vendor advisory: https://msrc.microsoft.com/update-guide/en-US/vulnerability/CVE-2021-43226
• Vulnerability database or vendor advisory: https://nvd.nist.gov/vuln/detail/CVE-2021-43226
• Vulnerability database or vendor advisory: https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-43226
• Vulnerability database or vendor advisory: https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-43226
• Vulnerability database or vendor advisory: https://www.cnnvd.org.cn/home/globalSearch?keyword=CNNVD-202112-1166

15 more references returned by Exploit Observer did not name this CVE or an alias, so they are left out.

VEDAS data as of 2026-11-01T17:12 UTC; fetched 2026-11-02.

Live scores

EPSS

0.033
some chance of attack soon

VEDAS

0.967
strong exploit evidence

On CISA KEV

Yes, since 2025-10-06

Detection rule

Out of scope (local)

Thin horizontal line: the “likely” (EPSS 0.10) or “strong” (VEDAS 0.90) threshold. Shaded “no data” areas are periods when cve-scores did not publish. The vertical line is the day CISA added it to its exploited list.

Who is affected

8 more products are listed in the CVE record.

Version ranges exactly as the CVE record states them. “Before X” means X is the first fixed version.

Exploit Observer also maps it to: microsoft windows_10_1507, microsoft windows_10_1607, microsoft windows_10_1809, microsoft windows_10_1909, microsoft windows_10_2004, microsoft windows_10_20h2, microsoft windows_10_21h1, microsoft windows_10_21h2, microsoft windows_11_21h2, microsoft windows_7.

How to fix it

Fixed versions stated in the CVE record: 10.0.17763.2366, 10.0.18363.1977, 10.0.19043.1415, 10.0.20348.405, 10.0.19041.1415, 10.0.19042.1415, 10.0.22000.376, 10.0.19044.1415, 10.0.10240.19145, 10.0.14393.4825, 6.1.7601.25796, 6.3.9600.20207 and others.

CISA required action: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

Vendor guidance:

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-43226
• https://nvd.nist.gov/vuln/detail/CVE-2021-43226

How to detect it

This bug needs local access to exploit. VEDAS signatures cover remotely exploitable bugs for now, so there is no network rule or remote check for it. Patch it and watch your endpoint telemetry for unusual local activity.

References

Government sources

• https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-43226 (government-resource)

Other references

• https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-43226 (x_refsource_MISC)

Other databases

• CVE record (cve.org)
• NVD
• Exploit Observer

Where this comes from

This advisory is generated automatically by VEDAS from: CVE.org record, CISA KEV, cve-scores (EPSS and VEDAS), Exploit Observer. Text in quotes is reproduced from the source; everything else is a fixed template filled with source fields. Nothing here is written by a language model. Check the vendor advisory before acting, and read how VEDAS and Exploit Observer work, and their limits.