CVE-2026-20927Network attack vectorHinoki check available

Authenticated service interruption via SMB race condition

Published Jan 13, 2026 · Updated Jan 13, 2026

Race condition in Microsoft Windows SMB Server allows remote authenticated users to interrupt service through crafted SMB traffic. Microsoft identifies concurrent use of a shared resource without proper synchronization, but has not disclosed the affected routine or object. Network access, SMB authentication, and winning a high-complexity race are required; successful exploitation interrupts SMB availability without reported data disclosure or modification.

CVSS severity5.3
Medium
EPSS probability0.92%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

Race condition in Microsoft Windows SMB Server allows remote authenticated users to interrupt service through crafted SMB traffic. Microsoft identifies concurrent use of a shared resource without proper synchronization, but has not disclosed the affected routine or object. Network access, SMB authentication, and winning a high-complexity race are required; successful exploitation interrupts SMB availability without reported data disclosure or modification.

The record

CVE
CVE-2026-20927
Published
Jan 13, 2026
Updated
Jan 13, 2026
Vendor
Microsoft
Product
Windows Server 2019
Classifications
CWE-362, T1499.004
Attack vector
network
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 vectornetwork
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 Server 2016 (Server Core installation)version=10.0.14393.0 <10.0.14393.8783
Microsoft · Windows 11, version 24H2version=10.0.26100.0 <10.0.26100.7623
Microsoft · Windows Server 2012 (Server Core installation)version=6.2.9200.0 <6.2.9200.25868
Microsoft · Windows Server 2012version=6.2.9200.0 <6.2.9200.25868
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 Server 2016version=10.0.14393.0 <10.0.14393.8783
Microsoft · Windows 11 Version 22H3version=10.0.22631.0 <10.0.22631.6491
Microsoft · Windows Server 2008 R2 Service Pack 1version=6.1.7601.0 <6.1.7601.28117
Microsoft · Windows Server 2008 R2 Service Pack 1 (Server Core installation)version=6.1.7601.0 <6.1.7601.28117
Microsoft · Windows 10 Version 22H2version=10.0.19045.0 <10.0.19045.6809
Microsoft · Windows Server 2012 R2 (Server Core installation)version=6.3.9600.0 <6.3.9600.22968
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 10 Version 1607version=10.0.14393.0 <10.0.14393.8783
Microsoft · Windows Server 2008 Service Pack 2version=6.0.6003.0 <6.0.6003.23717
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
Microsoft · Windows Server 2012 R2version=6.3.9600.0 <6.3.9600.22968
Microsoft · Windows Server 2008 Service Pack 2 (Server Core installation)version=6.0.6003.0 <6.0.6003.23717

Published CVSS scores

5.3Microsoft CorporationCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/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)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-362Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')
T1499.004Application or System Exploitation

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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