CVE-2026-20857

Local privilege escalation via untrusted pointer dereference

Published Jan 13, 2026 · Updated Jan 13, 2026

Untrusted pointer dereference in the Cloud Files Mini Filter Driver in Microsoft Windows allows local users to elevate privileges. The driver accepts a pointer value from an untrusted source and dereferences it, but Microsoft has not disclosed the affected routine or input path. A low-privileged local account can exploit the flaw without user interaction to obtain higher privileges and compromise system confidentiality, integrity, and availability.

CVSS severity7.8
High
EPSS probability0.48%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Untrusted pointer dereference in the Cloud Files Mini Filter Driver in Microsoft Windows allows local users to elevate privileges. The driver accepts a pointer value from an untrusted source and dereferences it, but Microsoft has not disclosed the affected routine or input path. A low-privileged local account can exploit the flaw without user interaction to obtain higher privileges and compromise system confidentiality, integrity, and availability.

The record

CVE
CVE-2026-20857
Published
Jan 13, 2026
Updated
Jan 13, 2026
Vendor
Microsoft
Product
Windows Server 2019
Classifications
CWE-822, T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Jan 13, 2026CVE publishedPublication date reported by the CVE source.
  2. Jan 13, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=10.0.17763.0 <10.0.17763.8276

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Microsoft · Windows Server 2019version=10.0.17763.0 <10.0.17763.8276
Microsoft · Windows Server 2025 (Server Core installation)version=10.0.26100.0 <10.0.26100.32230
Microsoft · Windows 11, version 25H2version=10.0.26200.0 <10.0.26200.7623
Microsoft · Windows 11, version 24H2version=10.0.26100.0 <10.0.26100.7623
Microsoft · Windows 10 Version 21H2version=10.0.19044.0 <10.0.19044.6809
Microsoft · Windows Server 2022, 23H2 Edition (Server Core installation)version=10.0.25398.0 <10.0.25398.2092
Microsoft · Windows 11 Version 22H3version=10.0.22631.0 <10.0.22631.6491
Microsoft · Windows 10 Version 22H2version=10.0.19045.0 <10.0.19045.6809
Microsoft · Windows Server 2019 (Server Core installation)version=10.0.17763.0 <10.0.17763.8276
Microsoft · Windows 11 Version 23H2version=10.0.22631.0 <10.0.22631.6491
Microsoft · Windows Server 2022version=10.0.20348.0 <10.0.20348.4648
Microsoft · Windows Server 2025version=10.0.26100.0 <10.0.26100.32230
Microsoft · Windows 10 Version 1809version=10.0.17763.0 <10.0.17763.8276

Published CVSS scores

7.8MicrosoftCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-822Untrusted Pointer Dereference
T1068Exploitation for Privilege Escalation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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