Is CVE-2026-20820 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-20820 being exploited in the wild.

How severe is CVE-2026-20820?

High severity, with a CVSS score of 7.8, published 13 January 2026.

Which products and versions are affected?

Microsoft Windows 11 22H3, 23H2, 24H2, 25H2; Microsoft Windows Server 2008 R2 Service Pack 1; Microsoft Windows 10 1607, 1809, 21H2, 22H2.

Is there a fix for CVE-2026-20820?

No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

How is CVE-2026-20820 attacked?

It is attacked with local access, in an operating system.

Am I affected by CVE-2026-20820?

Check whether you run Microsoft Windows 11, Microsoft Windows Server 2008 R2 or Microsoft Windows 10 at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-20820: Microsoft Windows CLFS Driver heap overflow privilege escalation

CVE-2026-20820 · Severity: high · CVSS 7.8 · Published 2026-01-13

A security vulnerability has been identified in the Windows Common Log File System (CLFS) Driver, a component that manages data logging for the operating system. An attacker who already has basic access to a computer could exploit this flaw to gain full administrative control over the system. This could allow them to view sensitive data, install malicious software, or disrupt business operations.

Technologies: Microsoft Windows 11, Microsoft Windows Server 2008 R2, Microsoft Windows 10. Vendors: Microsoft.

Quick answers

Is CVE-2026-20820 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-20820 being exploited in the wild.
How severe is CVE-2026-20820?: High severity, with a CVSS score of 7.8, published 13 January 2026.
Which products and versions are affected?: Microsoft Windows 11 22H3, 23H2, 24H2, 25H2; Microsoft Windows Server 2008 R2 Service Pack 1; Microsoft Windows 10 1607, 1809, 21H2, 22H2.
Is there a fix for CVE-2026-20820?: No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
How is CVE-2026-20820 attacked?: It is attacked with local access, in an operating system.
Am I affected by CVE-2026-20820?: Check whether you run Microsoft Windows 11, Microsoft Windows Server 2008 R2 or Microsoft Windows 10 at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

A heap-based buffer overflow vulnerability (CWE-122) exists in the Windows Common Log File System (CLFS) driver. The flaw is triggered when the driver improperly handles objects in memory, allowing a locally authenticated attacker with low privileges to execute code with SYSTEM-level permissions. The attack vector is local, requiring the attacker to run a specially crafted application on the target machine. Microsoft has released security updates to address this issue across various versions of Windows and Windows Server.

Affected products

Microsoft Windows 10 1607, 1809, 21H2, 22H2
Microsoft Windows 11 22H3, 23H2, 24H2, 25H2
Microsoft Windows Server 2008 R2 Service Pack 1

Timeline

2026-01-13: disclosed
2026-01-13: advisory

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-20820

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