Windows Common Log File System Driver Elevation of Privilege Vulnerability

CVE

CVE-2026-85870

Severity

Important

CVSS base score

7.0

CVSS vector

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

Impact

Elevation of Privilege

Exploitation detected

Not reported by MSRC

Publicly disclosed

No

Exploitability

Exploitation More Likely

Component

Windows Common Log File System Driver

Weakness

CWE-122: Heap-based Buffer Overflow

Issued by

Microsoft

Customer action

Required: apply the update

Affected products

Windows 10 Version 1607 for 32-bit Systems, Windows 10 Version 1607 for x64-based Systems, Windows 10 Version 1809 for 32-bit Systems, Windows 10 Version 1809 for x64-based Systems, Windows 10 Version 21H2 for 32-bit Systems, Windows 10 Version 21H2 for ARM64-based Systems, Windows 10 Version 21H2 for x64-based Systems, Windows 10 Version 22H2 for 32-bit Systems, Windows 10 Version 22H2 for ARM64-based Systems, Windows 10 Version 22H2 for x64-based Systems, Windows 11 Version 23H2 for ARM64-based Systems, Windows 11 Version 23H2 for x64-based Systems, Windows 11 Version 24H2 for ARM64-based Systems, Windows 11 Version 24H2 for x64-based Systems, Windows 11 Version 25H2 for ARM64-based Systems, Windows 11 Version 25H2 for x64-based Systems, Windows 11 Version 26H1 for ARM64-based Systems, Windows 11 version 26H1 for x64-based Systems, Windows 11 Version 26H2 for ARM64-based Systems, Windows 11 Version 26H2 for x64-based Systems, Windows Server 2012, Windows Server 2012 (Server Core installation), Windows Server 2012 R2, Windows Server 2012 R2 (Server Core installation), Windows Server 2016, Windows Server 2016 (Server Core installation), Windows Server 2019, Windows Server 2019 (Server Core installation), Windows Server 2022, Windows Server 2022 (Server Core installation), Windows Server 2025, Windows Server 2025 (Server Core installation)

Updates that fix it

KB5126646: Windows Server 2025, Windows Server 2025 (Server Core installation) (restart required); KB5126651: Windows 10 Version 1809 for 32-bit Systems, Windows 10 Version 1809 for x64-based Systems, Windows Server 2019, Windows Server 2019 (Server Core installation) (restart required); KB5126653: Windows 11 Version 23H2 for ARM64-based Systems, Windows 11 Version 23H2 for x64-based Systems (restart required); KB5126655: Windows Server 2022, Windows Server 2022 (Server Core installation) (restart required); KB5126657: Windows 10 Version 21H2 for 32-bit Systems, Windows 10 Version 21H2 for ARM64-based Systems, Windows 10 Version 21H2 for x64-based Systems, Windows 10 Version 22H2 for 32-bit Systems, Windows 10 Version 22H2 for ARM64-based Systems, Windows 10 Version 22H2 for x64-based Systems (restart required); KB5126835: Windows Server 2012, Windows Server 2012 (Server Core installation) (restart required); KB5126836: Windows Server 2012 R2, Windows Server 2012 R2 (Server Core installation) (restart required); KB5126868: Windows 10 Version 1607 for 32-bit Systems, Windows 10 Version 1607 for x64-based Systems, Windows Server 2016, Windows Server 2016 (Server Core installation) (restart required); KB5127646: Windows 11 Version 26H1 for ARM64-based Systems, Windows 11 version 26H1 for x64-based Systems (restart required); KB5127648: Windows 11 Version 24H2 for ARM64-based Systems, Windows 11 Version 24H2 for x64-based Systems, Windows 11 Version 25H2 for ARM64-based Systems, Windows 11 Version 25H2 for x64-based Systems, Windows 11 Version 26H2 for ARM64-based Systems, Windows 11 Version 26H2 for x64-based Systems (restart required)

CISA KEV

Not listed in the collected catalog

EPSS

0.3%; scored 20 Oct 2026

Public exploit code

No Nuclei template listed

Published

13 Oct 2026 07:00 UTC

Last revised

14 Oct 2026 07:00 UTC

Revision note

Updated an acknowledgement. This is an informational change only.

• MSRC advisory
• NVD
• CVE.org
• October 2026
• KB5126646
• KB5126651
• KB5126653
• KB5126655
• KB5126657
• KB5126835
• KB5126836
• KB5126868
• KB5127646
• KB5127648
• Cisco Talos analysis

Microsoft security releases

Complete at observationRead 20 Oct 2026 at 20:53 UTC

CISA KEV

Complete at observationRead 20 Oct 2026 at 20:53 UTC

FIRST EPSS

Complete at observationRead 20 Oct 2026 at 20:53 UTC

Public exploit code

Complete at observationRead 20 Oct 2026 at 20:53 UTC

Coverage describes the sources at this observation. A complete read then does not establish their current position.

1. 20 Oct 2026 · 20:53:31 UTC EPSS0.3%; scored 19 Oct 2026 → 0.3%; scored 20 Oct 2026
2. 19 Oct 2026 · 15:12:40 UTC EPSS0.3%; scored 18 Oct 2026 → 0.3%; scored 19 Oct 2026
3. 19 Oct 2026 · 15:12:40 UTC Link: Cisco Talos analysishttps://blog.talosintelligence.com/microsoft-patch-tuesday-for-october-2026
4. 18 Oct 2026 · 14:54:30 UTC EPSS0.3%; scored 16 Oct 2026 → 0.3%; scored 18 Oct 2026
5. 18 Oct 2026 · 14:54:30 UTC Link: October 2026/security?release=2026-Oct#cves
6. 16 Oct 2026 · 16:13:25 UTC EPSS0.3%; scored 15 Oct 2026 → 0.3%; scored 16 Oct 2026
7. 15 Oct 2026 · 21:30:54 UTC EPSS0.3%; scored 14 Oct 2026 → 0.3%; scored 15 Oct 2026
8. 15 Oct 2026 · 01:07:54 UTC EPSSNot scored → 0.3%; scored 14 Oct 2026
9. 14 Oct 2026 · 15:58:54 UTC Revision noteInformation published. → Updated an acknowledgement. This is an informational change only.
10. 14 Oct 2026 · 15:58:54 UTC Last revised13 Oct 2026 07:00 UTC → 14 Oct 2026 07:00 UTC

The most recent 100 field changes are listed. Complete recorded revisions are kept separately.

Cite this recorded revision to keep the same title, summary, facts and links when the page changes.

A day selects the latest observation by the end of that UTC day; today's selection can change until midnight. History starts when this installation records it.