CVE-2026-23666: .NET Framework Denial of Service Vulnerability

Published Apr 14, 2026
·
Updated

.NET Framework Denial of Service Vulnerability

Other sources

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

— Microsoft

Affected Software

68 affected componentsFixes available
All of the following
Microsoft .NET Framework=3.5
Any of the following
Microsoft Windows Server 2012
Microsoft Windows Server 2012=r2
All of the following
Any of the following
Microsoft .NET Framework=3.5
Microsoft .NET Framework=4.7.2
Any of the following
Microsoft Windows 10 1809
Microsoft Windows 10 1809
Microsoft Windows 10 1809
All of the following
Any of the following
Microsoft .NET Framework=3.5
Microsoft .NET Framework=4.8
Any of the following
Microsoft Windows 10 1809
Microsoft Windows 10 1809
Microsoft Windows 10 1809
Microsoft Windows 10 21h2
Microsoft Windows 10 21h2
Microsoft Windows 10 21h2
Microsoft Windows 10 22h2
Microsoft Windows 10 22h2
Microsoft Windows 10 22h2
Microsoft Windows Server 2022
All of the following
Any of the following
Microsoft .NET Framework=3.5
Microsoft .NET Framework=4.8.1
Any of the following
Microsoft Windows 10 21h2
Microsoft Windows 10 21h2
Microsoft Windows 10 21h2
Microsoft Windows 10 22h2
Microsoft Windows 10 22h2
Microsoft Windows 10 22h2
Microsoft Windows 11 22h2
Microsoft Windows 11 22h2
Microsoft Windows 11 23h2
Microsoft Windows 11 23h2
Microsoft Windows 11 24h2
Microsoft Windows 11 24h2
Microsoft Windows 11 25h2
Microsoft Windows 11 25h2
Microsoft Windows 11 26h1
Microsoft Windows 11 26h1
Microsoft Windows Server 2022
Microsoft Windows Server 2022 23h2
Microsoft Windows Server 2025
All of the following
Any of the following
Microsoft .NET Framework=4.6.2
Microsoft .NET Framework=4.7
Microsoft .NET Framework=4.7.1
Microsoft .NET Framework=4.7.2
Any of the following
Microsoft Windows Server 2012
Microsoft Windows Server 2012=r2
All of the following
Microsoft .NET Framework=4.8
Any of the following
Microsoft Windows 10 1607
Microsoft Windows 10 1607
Microsoft Windows Server 2012
Microsoft Windows Server 2012=r2
Microsoft .NET Framework=3.5, =4.8.1
2.0.50727.9181 & 3.0.30729.9165 & 4.8.9332.0
Microsoft .NET Framework=3.5, =4.8.1
2.0.50727.9181 & 3.0.30729.9165 & 4.8.9332.0
Microsoft .NET Framework=3.5
2.0.50727.8982 & 3.0.30729.8976
Microsoft .NET Framework=3.5, =4.8.1
2.0.50727.9181 & 3.0.30729.9165 & 4.8.9332.0
Microsoft .NET Framework=3.5
2.0.50727.8982 & 3.0.30729.8976
Microsoft .NET Framework=3.5, =4.8.1
2.0.50727.9181 & 3.0.30729.9165 & 4.8.9332.0
Microsoft .NET Framework=3.5, =4.8.1
2.0.50727.9181 & 3.0.30729.9165 & 4.8.9332.0
Microsoft .NET Framework=4.8
4.8.4801.0
Microsoft .NET Framework=4.6.2, =4.7, =4.7.1, =4.7.2
4.8.4801.0
Microsoft .NET Framework=4.6.2, =4.7, =4.7.1, =4.7.2
4.7.4141.0
Microsoft .NET Framework=3.5, =4.7.2
2.0.50727.9068 & 3.0.30729.9065 & 4.7.4141.0
Microsoft .NET Framework=3.5, =4.8
2.0.50727.9181 & 3.0.30729.9165 & 4.8.4801.0
Microsoft .NET Framework=3.5, =4.8
2.0.50727.9181 & 3.0.30729.9165 & 4.8.4801.0
Microsoft .NET Framework=3.5, =4.8
2.0.50727.9068 & 3.0.30729.9065 & 4.8.4801.0
Microsoft .NET Framework=4.8
4.8.4801.0
Microsoft .NET Framework=4.8
4.8.4801.0

Remediation

Recommended actions to resolve this vulnerability, in priority order.

  1. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 2.0.50727.9181 & 3.0.30729.9165 & 4.8.9332.0Patch KB5082421
  2. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 2.0.50727.9181 & 3.0.30729.9165 & 4.8.9332.0Patch KB5082417
  3. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 2.0.50727.8982 & 3.0.30729.8976Patch KB5082398
  4. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 2.0.50727.9181 & 3.0.30729.9165 & 4.8.9332.0Patch KB5082420
  5. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 2.0.50727.8982 & 3.0.30729.8976Patch KB5082406
  6. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 2.0.50727.9181 & 3.0.30729.9165 & 4.8.9332.0Patch KB5082424
  7. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 2.0.50727.9181 & 3.0.30729.9165 & 4.8.9332.0Patch KB5082418
  8. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 2.0.50727.9181 & 3.0.30729.9165 & 4.8.9332.0Patch KB5082419
  9. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 4.8.4801.0Patch KB5082411
  10. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 4.8.4801.0Patch KB5082400
  11. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 4.7.4141.0Patch KB5082402
  12. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 2.0.50727.9181 & 3.0.30729.9165 & 4.8.9332.0Patch KB5082425
  13. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 2.0.50727.9181 & 3.0.30729.9165 & 4.8.4801.0Patch KB5082426
  14. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 2.0.50727.9068 & 3.0.30729.9065 & 4.7.4141.0Patch KB5082413
  15. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 2.0.50727.9181 & 3.0.30729.9165 & 4.8.4801.0Patch KB5082427
  16. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 2.0.50727.9068 & 3.0.30729.9065 & 4.8.4801.0Patch KB5082414
  17. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 4.8.4801.0Patch KB5082404
  18. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 4.8.4801.0Patch KB5082403

Event History

Apr 14, 2026
CVE Published
via Microsoft·02:00 PM
Data Sourced
via Microsoft·02:00 PM
DescriptionSeverityWeakness
Data Sourced
via Microsoft·02:00 PM
Affected Software
Updated
via Microsoft·02:00 PM
Description
CVE Published
via MITRE·04:57 PM
Data Sourced
via MITRE·04:57 PM
DescriptionSeverity
Data Sourced
via Red Hat·06:02 PM
DescriptionSeverityAffected Software
Data Sourced
via NVD·06:16 PM
DescriptionSeverityWeaknessAffected Software
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Frequently Asked Questions

1

What is the severity of CVE-2026-23666?

CVE-2026-23666 is classified as a Denial of Service vulnerability.

2

How do I fix CVE-2026-23666?

To fix CVE-2026-23666, you should apply the recommended security patches available for affected .NET Framework versions.

3

Which .NET Framework versions are affected by CVE-2026-23666?

CVE-2026-23666 affects .NET Framework versions 3.5 and 4.8.1.

4

What causes the denial of service in CVE-2026-23666?

CVE-2026-23666 is caused by race conditions due to improper synchronization while executing concurrent tasks.

5

Can CVE-2026-23666 be exploited remotely?

Yes, CVE-2026-23666 can be exploited remotely by unauthorized attackers to deny service.

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