NVD

CVE-2026-23666 Detail

Modified After Enrichment

This CVE record has been updated after NVD enrichment efforts were completed. Enrichment data supplied by the NVD may require amendment due to these changes.

Description

Improper input validation in .NET Framework allows an unauthorized attacker to deny service over a network.

Metrics

NVD enrichment efforts reference publicly available information to associate vector strings. CVSS information contributed by other sources is also displayed.

CVSS 4.0 Severity and Vector Strings:

NIST: NVD

N/A

NVD assessment not yet provided.

CVSS 3.x Severity and Vector Strings:

Nist CVSS score does not match with CNA score

CNA: Microsoft Corporation

Base Score: 7.5 HIGH

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

ADP: redhat-SADP

Base Score: 7.5 HIGH

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS 2.0 Severity and Vector Strings:

National Institute of Standards and Technology

NIST: NVD

Base Score: N/A

NVD assessment not yet provided.

References to Advisories, Solutions, and Tools

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URL	Source(s)	Tag(s)
https://access.redhat.com/security/cve/CVE-2026-23666	redhat-SADP
https://bugzilla.redhat.com/show_bug.cgi?id=2458271	redhat-SADP
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-23666	Microsoft Corporation	Vendor Advisory
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-23666.json	redhat-SADP

Weakness Enumeration

CWE-ID	CWE Name	Source
CWE-366	Race Condition within a Thread	redhat-SADP
CWE-755	Improper Handling of Exceptional Conditions	Microsoft Corporation

Known Affected Software Configurations Switch to CPE 2.2

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Change History

6 change records found show changes

CVE Modified by redhat-SADP 6/29/2026 11:17:33 PM

Action	Type	New Value
Added	CVSS V3.1	AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Added	CWE	CWE-366
Added	Reference	https://access.redhat.com/security/cve/CVE-2026-23666
Added	Reference	https://bugzilla.redhat.com/show_bug.cgi?id=2458271
Added	Reference	https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-23666.json
Added	Affected	[{"vendor":"Red Hat","product":"Red Hat Enterprise Linux 10","defaultStatus":"unaffected","cpes":["cpe:/o:redhat:enterprise_linux:10"]},{"vendor":"Red Hat","product":"Red Hat Enterprise Linux 8","defaultStatus":"unaffected","cpes":["cpe:/o:redhat:enterprise_linux:8"]},{"vendor":"Red Hat","product":"Red Hat Enterprise Linux 9","defaultStatus":"unaffected","cpes":["cpe:/o:redhat:enterprise_linux:9"]},{"vendor":"Red Hat","product":"Red Hat Hardened Images","defaultStatus":"unaffected","cpes":["cpe:/a:redhat:hummingbird:1"]}]

CVE Modified by Microsoft Corporation 6/17/2026 6:21:55 AM

Action

Type

Old Value

New Value

Added

Affected

Record truncated, showing 2048 of 3399 characters.
View Entire Change Record

[{"vendor":"Microsoft","product":"Microsoft .NET Framework 3.5","platforms":["Windows Server 2012","Windows Server 2012 (Server Core installation)","Windows Server 2012 R2","Windows Server 2012 R2 (Server Core installation)"],"versions":[{"version":"3.5.0","lessThan":"2.0.50727.8982 & 3.0.30729.8976","versionType":"custom","status":"affected"}]},{"vendor":"Microsoft","product":"Microsoft .NET Framework 3.5 AND 4.7.2","platforms":["Windows 10 Version 1809 for 32-bit Systems","Windows 10 Version 1809 for ARM64-based Systems","Windows 10 Version 1809 for x64-based Systems"],"versions":[{"version":"4.7.0","lessThan":"2.0.50727.9068 & 3.0.30729.9065 & 4.7.4141.0","versionType":"custom","status":"affected"}]},{"vendor":"Microsoft","product":"Microsoft .NET Framework 3.5 AND 4.8","platforms":["Windows 10 Version 1809 for 32-bit Systems","Windows 10 Version 1809 for ARM64-based 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 Server 2022","Windows Server 2022 (Server Core installation)"],"versions":[{"version":"4.8.0","lessThan":"2.0.50727.9068 & 3.0.30729.9065 & 4.8.4801.0","versionType":"custom","status":"affected"}]},{"vendor":"Microsoft","product":"Microsoft .NET Framework 3.5 AND 4.8.1","platforms":["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 22H2 for ARM64-based Systems","Windows 11 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 System

Initial Analysis by NIST 5/07/2026 3:46:16 PM

Action	Type	New Value
Added	CPE Configuration	AND OR cpe:2.3:a:microsoft:.net_framework:3.5:-::::::* cpe:2.3:a:microsoft:.net_framework:4.8.1::::::: OR cpe:2.3:o:microsoft:windows_server_2022:-:::::::* cpe:2.3:o:microsoft:windows_11_22h2:-::::::x64: cpe:2.3:o:microsoft:windows_10_21h2:-::::::x64: cpe:2.3:o:microsoft:windows_10_22h2:-::::::x64: cpe:2.3:o:microsoft:windows_10_21h2:-::::::arm64: cpe:2.3:o:microsoft:windows_10_21h2:-::::::x86: cpe:2.3:o:microsoft:windows_10_22h2:-::::::arm64: cpe:2.3:o:microsoft:windows_10_22h2:-::::::x86: cpe:2.3:o:microsoft:windows_11_22h2:-::::::arm64: cpe:2.3:o:microsoft:windows_11_23h2:-::::::arm64: cpe:2.3:o:microsoft:windows_11_23h2:-::::::x64: cpe:2.3:o:microsoft:windows_11_24h2:-::::::x64: cpe:2.3:o:microsoft:windows_11_24h2:-::::::arm64: cpe:2.3:o:microsoft:windows_server_2022_23h2:-::::::x64: cpe:2.3:o:microsoft:windows_11_25h2:-::::::arm64: cpe:2.3:o:microsoft:windows_11_25h2:-::::::x64: cpe:2.3:o:microsoft:windows_11_26h1:-::::::arm64: cpe:2.3:o:microsoft:windows_11_26h1:-::::::x64: cpe:2.3:o:microsoft:windows_server_2025:-::::::x64:
Added	CPE Configuration	AND OR cpe:2.3:a:microsoft:.net_framework:3.5:-::::::* OR cpe:2.3:o:microsoft:windows_server_2012:r2:::::::* cpe:2.3:o:microsoft:windows_server_2012:-:::::::*
Added	CPE Configuration	AND OR cpe:2.3:a:microsoft:.net_framework:4.6.2::::::: cpe:2.3:a:microsoft:.net_framework:4.7::::::: cpe:2.3:a:microsoft:.net_framework:4.7.1::::::: cpe:2.3:a:microsoft:.net_framework:4.7.2::::::: OR cpe:2.3:o:microsoft:windows_server_2012:r2:::::::* cpe:2.3:o:microsoft:windows_server_2012:-:::::::*
Added	CPE Configuration	AND OR cpe:2.3:a:microsoft:.net_framework:4.7.2::::::: cpe:2.3:a:microsoft:.net_framework:3.5:-::::::* OR cpe:2.3:o:microsoft:windows_10_1809:-::::::x64: cpe:2.3:o:microsoft:windows_10_1809:-::::::arm64: cpe:2.3:o:microsoft:windows_10_1809:-::::::x86:
Added	CPE Configuration	AND OR cpe:2.3:a:microsoft:.net_framework:4.8::::::: cpe:2.3:a:microsoft:.net_framework:3.5:-::::::* OR cpe:2.3:o:microsoft:windows_server_2022:-:::::::* cpe:2.3:o:microsoft:windows_10_1809:-::::::x64: cpe:2.3:o:microsoft:windows_10_21h2:-::::::x64: cpe:2.3:o:microsoft:windows_10_22h2:-::::::x64: cpe:2.3:o:microsoft:windows_10_21h2:-::::::arm64: cpe:2.3:o:microsoft:windows_10_21h2:-::::::x86: cpe:2.3:o:microsoft:windows_10_22h2:-::::::arm64: cpe:2.3:o:microsoft:windows_10_1809:-::::::arm64: cpe:2.3:o:microsoft:windows_10_1809:-::::::x86: cpe:2.3:o:microsoft:windows_10_22h2:-::::::x86:
Added	CPE Configuration	AND OR cpe:2.3:a:microsoft:.net_framework:4.8::::::: OR cpe:2.3:o:microsoft:windows_server_2012:r2:::::::* cpe:2.3:o:microsoft:windows_server_2012:-:::::::* cpe:2.3:o:microsoft:windows_10_1607:-::::::x64: cpe:2.3:o:microsoft:windows_10_1607:-::::::x86:
Added	Reference Type	Microsoft Corporation: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-23666 Types: Vendor Advisory

New CVE Received from Microsoft Corporation 4/14/2026 2:16:44 PM

Action	Type	New Value
Added	Description	Concurrent execution using shared resource with improper synchronization ('race condition') in .NET Framework allows an unauthorized attacker to deny service over a network.
Added	CVSS V3.1	AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Added	CWE	CWE-755
Added	Reference	https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-23666

Quick Info

CVE Dictionary Entry:
CVE-2026-23666
NVD Published Date:
04/14/2026
NVD Last Modified:
06/29/2026
Source:
Microsoft Corporation

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National Vulnerability Database