CVE-2021-43226Exploited in the wildNVD status: Analyzed
Microsoft Windows Privilege Escalation
CVE-2021-43226 is a high-severity vulnerability in Windows 10 Version 1809 from Microsoft, with a CVSS 3.1 base score of 7.8 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. The record lists version 10.0.17763.2366 as the first without the flaw, so updating Windows 10 Version 1809 to that release or later removes the exposure. CISA added it to the Known Exploited Vulnerabilities catalogue on October 6, 2025, which means attacks have been observed in the wild, including in ransomware campaigns.
Patch now
Attackers are already exploiting this vulnerability, according to CISA.
What to do
- Update Windows 10 Version 1809 to 10.0.17763.2366 or a later version.
- Update Windows Server 2019 to 10.0.17763.2366 or a later version.
- Update Windows Server 2019 (Server Core installation) to 10.0.17763.2366 or a later version.
- CISA's 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.
- Read the advisory on portal.msrc.microsoft.com for workarounds and exact fixed builds.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Microsoft | Windows 10 Version 1809 | 10.0.0 up to, but not including, 10.0.17763.2366 | 10.0.17763.2366 |
| Microsoft | Windows Server 2019 | 10.0.0 up to, but not including, 10.0.17763.2366 | 10.0.17763.2366 |
| Microsoft | Windows Server 2019 (Server Core installation) | 10.0.0 up to, but not including, 10.0.17763.2366 | 10.0.17763.2366 |
| Microsoft | Windows 10 Version 1909 | 10.0.0 up to, but not including, 10.0.18363.1977 | 10.0.18363.1977 |
| Microsoft | Windows 10 Version 21H1 | 10.0.0 up to, but not including, 10.0.19043.1415 | 10.0.19043.1415 |
| Microsoft | Windows Server 2022 | 10.0.0 up to, but not including, 10.0.20348.405 | 10.0.20348.405 |
| Microsoft | Windows 10 Version 2004 | 10.0.0 up to, but not including, 10.0.19041.1415 | 10.0.19041.1415 |
| Microsoft | Windows Server version 2004 | 10.0.0 up to, but not including, 10.0.19041.1415 | 10.0.19041.1415 |
| Microsoft | Windows 10 Version 20H2 | 10.0.0 up to, but not including, 10.0.19042.1415 | 10.0.19042.1415 |
| Microsoft | Windows Server version 20H2 | 10.0.0 up to, but not including, 10.0.19042.1415 | 10.0.19042.1415 |
| Microsoft | Windows 11 version 21H2 | 10.0.0 up to, but not including, 10.0.22000.376 | 10.0.22000.376 |
| Microsoft | Windows 10 Version 21H2 | 10.0.0 up to, but not including, 10.0.19044.1415 | 10.0.19044.1415 |
| Microsoft | Windows 10 Version 1507 | 10.0.0 up to, but not including, 10.0.10240.19145 | 10.0.10240.19145 |
| Microsoft | Windows 10 Version 1607 | 10.0.0 up to, but not including, 10.0.14393.4825 | 10.0.14393.4825 |
| Microsoft | Windows Server 2016 | 10.0.0 up to, but not including, 10.0.14393.4825 | 10.0.14393.4825 |
| Microsoft | Windows Server 2016 (Server Core installation) | 10.0.0 up to, but not including, 10.0.14393.4825 | 10.0.14393.4825 |
| Microsoft | Windows 7 | 6.1.0 up to, but not including, 6.1.7601.25796 | 6.1.7601.25796 |
| Microsoft | Windows 7 Service Pack 1 | 6.1.0 up to, but not including, 6.1.7601.25796 | 6.1.7601.25796 |
| Microsoft | Windows 8.1 | 6.3.0 up to, but not including, 6.3.9600.20207 | 6.3.9600.20207 |
| Microsoft | Windows Server 2008 Service Pack 2 | 6.0.0 up to, but not including, 6.0.6003.21309 | 6.0.6003.21309 |
| Microsoft | Windows Server 2008 Service Pack 2 (Server Core installation) | 6.0.0 up to, but not including, 6.0.6003.21309 | 6.0.6003.21309 |
| Microsoft | Windows Server 2008 R2 Service Pack 1 | 6.1.0 up to, but not including, 6.1.7601.25796 | 6.1.7601.25796 |
| Microsoft | Windows Server 2008 R2 Service Pack 1 (Server Core installation) | 6.0.0 up to, but not including, 6.1.7601.25796 | 6.1.7601.25796 |
| Microsoft | Windows Server 2012 | 6.2.0 up to, but not including, 6.2.9200.23545; 6.2.0 up to, but not including, 6.2.9200.23540 | 6.2.9200.23545, 6.2.9200.23540 |
| Microsoft | Windows Server 2012 (Server Core installation) | 6.2.0 up to, but not including, 6.2.9200.23545; 6.2.0 up to, but not including, 6.2.9200.23540 | 6.2.9200.23545, 6.2.9200.23540 |
Version data comes from the organisation that assigned the CVE; 15 further products are omitted here. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- LocalThe attacker needs local access or must trick a user into running something.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 7.8 | High | CNA (microsoft.com) |
| CVSS 3.1 | 7.8 | High | NVD |
| CVSS 2.0 | 4.6 | Medium | NVD |
Official description
Windows Common Log File System Driver Elevation of Privilege Vulnerability
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: active, automatable: no, technical impact: total).
- Added to CISA's Known Exploited Vulnerabilities catalogue.
- Deadline for US federal agencies to remediate, set by CISA.
- Record last changed materially (score, affected products, status or references).
References
Third-party and government advisories
- cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-43226US Government Resource
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