.NET Framework Denial of Service Vulnerability

Summary

CVE	CVE-2026-23666
State	PUBLISHED
Assigner	microsoft
Source Priority	CVE Program / NVD first with legacy fallback
Published	2026-04-14 18:16:44 UTC
Updated	2026-07-15 02:18:43 UTC
Description	Improper input validation in .NET Framework allows an unauthorized attacker to deny service over a network.

Risk And Classification

Primary CVSS: v3.1 7.5 HIGH from ADP

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

EPSS: 0.001060000 probability, percentile 0.285690000 (date 2026-04-21)

Problem Types: CWE-755 | CWE-366 | CWE-755 CWE-755: Improper Handling of Exceptional Conditions | CWE-366 Race Condition within a Thread

Version	Source	Type	Score	Severity	Vector
3.1	ADP	CVSS	7.5	HIGH	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`
3.1	[email protected]	Secondary	7.5	HIGH	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`
3.1	0b0ca135-0b70-47e7-9f44-1890c2a1c46c	Secondary	7.5	HIGH	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`
3.1	CNA	CVSS	7.5	HIGH	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:P/RL:O/RC:C`

CVSS v3.1 Breakdown

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

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

NVD Known Affected Configurations (CPE 2.3)

Type	Vendor	Product	Version	Update	Edition	Language
Application	Microsoft	.net Framework	3.5	-	All	All
Operating System	Microsoft	Windows Server 2012	-	All	All	All
Operating System	Microsoft	Windows Server 2012	r2	All	All	All

Vendor Declared Affected Products

Source	Vendor	Product	Version	Platforms
CNA	Microsoft	Microsoft .NET Framework 3.5	affected 3.5.0 2.0.50727.8982 & 3.0.30729.8976 custom	Windows Server 2012, Windows Server 2012 (Server Core installation), Windows Server 2012 R2, Windows Server 2012 R2 (Server Core installation)
CNA	Microsoft	Microsoft .NET Framework 3.5 AND 4.7.2	affected 4.7.0 2.0.50727.9068 & 3.0.30729.9065 & 4.7.4141.0 custom	Windows 10 Version 1809 for 32-bit Systems, Windows 10 Version 1809 for ARM64-based Systems, Windows 10 Version 1809 for x64-based Systems
CNA	Microsoft	Microsoft .NET Framework 3.5 AND 4.8	affected 4.8.0 2.0.50727.9068 & 3.0.30729.9065 & 4.8.4801.0 custom	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)
CNA	Microsoft	Microsoft .NET Framework 3.5 AND 4.8.1	affected 4.8.1 2.0.50727.9181 & 3.0.30729.9165 & 4.8.9332.0 custom	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 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 Server 2022, Windows Server 2022 (Server Core installation), Windows Server 2022, 23H2 Edition (Server Core installation), Windows Server 2025, Windows Server 2025 (Server Core installation)
CNA	Microsoft	Microsoft .NET Framework 4.6.2/4.7/4.7.1/4.7.2	affected 4.7.0 4.8.4801.0 custom	Windows Server 2012, Windows Server 2012 (Server Core installation), Windows Server 2012 R2, Windows Server 2012 R2 (Server Core installation)
CNA	Microsoft	Microsoft .NET Framework 4.8	affected 4.8.0 4.8.4801.0 custom	Windows 10 Version 1607 for 32-bit Systems, Windows 10 Version 1607 for x64-based Systems, Windows Server 2012, Windows Server 2012 (Server Core installation), Windows Server 2012 R2, Windows Server 2012 R2 (Server Core installation)
ADP	Red Hat	Red Hat Enterprise Linux 10	Not specified	Not specified
ADP	Red Hat	Red Hat Enterprise Linux 10	Not specified	Not specified
ADP	Red Hat	Red Hat Enterprise Linux 10	Not specified	Not specified
ADP	Red Hat	Red Hat Enterprise Linux 8	Not specified	Not specified
ADP	Red Hat	Red Hat Enterprise Linux 8	Not specified	Not specified
ADP	Red Hat	Red Hat Enterprise Linux 8	Not specified	Not specified
ADP	Red Hat	Red Hat Enterprise Linux 9	Not specified	Not specified
ADP	Red Hat	Red Hat Enterprise Linux 9	Not specified	Not specified
ADP	Red Hat	Red Hat Enterprise Linux 9	Not specified	Not specified
ADP	Red Hat	Red Hat Hardened Images	Not specified	Not specified
ADP	Red Hat	Red Hat Hardened Images	Not specified	Not specified
ADP	Red Hat	Red Hat Hardened Images	Not specified	Not specified

References

Reference	Source	Link	Tags
bugzilla.redhat.com/show_bug.cgi	0b0ca135-0b70-47e7-9f44-1890c2a1c46c	bugzilla.redhat.com
access.redhat.com/security/cve/CVE-2026-23666	0b0ca135-0b70-47e7-9f44-1890c2a1c46c	access.redhat.com
msrc.microsoft.com/update-guide/vulnerability/CVE-2026-23666	[email protected]	msrc.microsoft.com	Vendor Advisory
security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-23666.json	0b0ca135-0b70-47e7-9f44-1890c2a1c46c	security.access.redhat.com
CVE Program record	CVE.ORG	www.cve.org	canonical
NVD vulnerability detail	NVD	nvd.nist.gov	canonical, analysis

No vendor comments have been submitted for this CVE.

Additional Advisory Data

Source	Time	Event
ADP	2026-04-14T18:01:54.434Z	Reported to Red Hat.
ADP	2026-04-14T16:57:53.069Z	Made public.

There are currently no legacy QID mappings associated with this CVE.