CVE-2026-84008
High CVSS 7.5Published 2026-10-13 ยท last changed 2026-10-13
The fix
Microsoft fixes this in updatesKB5126868, KB5127666, KB5127689, KB5127692, KB5127690, KB5127694, KB5127693, KB5127685, KB5127683, KB5127687, KB5127696, KB5127660, KB5127664, KB5127667, KB5127668, KB5127691, KB5127684, KB5127686, KB5127688. The fixed build differs per Windows version, so the row that matters is the one matching the machine you are looking at.
| Windows version | Fixed in build | Update | Released |
|---|---|---|---|
| Microsoft .NET Framework 3.5 AND 4.6.2/4.7/4.7.1/4.7.2 on Windows 10 version 1607 | 2.0.50727.8987 AND 3.0.30729.8982 AND 4.7.4150.0 | KB5126868 | 2026-10-13 |
| Microsoft .NET Framework 3.5 AND 4.6.2/4.7/4.7.1/4.7.2 on Windows Server 2016 | 2.0.50727.8987 AND 3.0.30729.8982 AND 4.7.4150.0 | KB5126868 | 2026-10-13 |
| Microsoft .NET Framework 3.5 AND 4.6.2/4.7/4.7.1/4.7.2 on Windows Server 2019 | 2.0.50727.9073 AND 3.0.30729.9070 AND 4.7.4150.0 | KB5127666 | 2026-10-13 |
| Microsoft .NET Framework 3.5 AND 4.7.2 on Windows 10 version 1809 | 2.0.50727.9073 AND 3.0.30729.9070 AND 4.7.4150.0 | KB5127666 | 2026-10-13 |
| Microsoft .NET Framework 3.5 AND 4.8.1 on Windows 10 version 21H2 | 2.0.50727.9188 AND 3.0.30729.9171 AND 4.8.9363.0 | KB5127689 | 2026-10-13 |
| Microsoft .NET Framework 3.5 AND 4.8.1 on Windows 10 version 22H2 | 2.0.50727.9188 AND 3.0.30729.9171 AND 4.8.9363.0 | KB5127689 | 2026-10-13 |
| Microsoft .NET Framework 3.5 AND 4.8.1 on Windows 11 version 23H2 | 2.0.50727.9188 AND 3.0.30729.9171 AND 4.8.9363.0 | KB5127692 | 2026-10-13 |
| Microsoft .NET Framework 3.5 AND 4.8.1 on Windows 11 version 24H2 | 2.0.50727.9188 AND 3.0.30729.9171 AND 4.8.9363.0 | KB5127690 | 2026-10-13 |
| Microsoft .NET Framework 3.5 AND 4.8.1 on Windows 11 version 25H2 | 2.0.50727.9188 AND 3.0.30729.9171 AND 4.8.9363.0 | KB5127690 | 2026-10-13 |
| Microsoft .NET Framework 3.5 AND 4.8.1 on Windows 11 version 26H2 | 2.0.50727.9188 AND 3.0.30729.9171 AND 4.8.10008.0 | KB5127694 | 2026-10-13 |
| Microsoft .NET Framework 3.5 AND 4.8.1 on Windows Server 2022 | 2.0.50727.9188 AND 3.0.30729.9171 AND 4.8.9363.0 | KB5127693 | 2026-10-13 |
| Microsoft .NET Framework 3.5 AND 4.8.1 on Windows Server 2025 | 2.0.50727.9188 AND 3.0.30729.9171 AND 4.8.9363.0 | KB5127690 | 2026-10-13 |
| Microsoft .NET Framework 3.5 AND 4.8 on Windows 10 version 1809 | 2.0.50727.9073 AND 3.0.30729.9070 AND 4.8.4811.0 | KB5127685 | 2026-10-13 |
| Microsoft .NET Framework 3.5 AND 4.8 on Windows 10 version 21H2 | 2.0.50727.9188 AND 3.0.30729.9171 AND 4.8.4811.0 | KB5127683 | 2026-10-13 |
| Microsoft .NET Framework 3.5 AND 4.8 on Windows 10 version 22H2 | 2.0.50727.9188 AND 3.0.30729.9171 AND 4.8.4811.0 | KB5127683 | 2026-10-13 |
| Microsoft .NET Framework 3.5 AND 4.8 on Windows Server 2019 | 2.0.50727.9073 AND 3.0.30729.9070 AND 4.8.4811.0 | KB5127685 | 2026-10-13 |
| Microsoft .NET Framework 3.5 AND 4.8 on Windows Server 2022 | 2.0.50727.9188 AND 3.0.30729.9171 AND 4.8.4811.0 | KB5127687 | 2026-10-13 |
| Microsoft .NET Framework 3.5 on Windows 11 version 26H1 | 2.0.50727.9188 AND 3.0.30729.9171 | KB5127696 | 2026-10-13 |
| Microsoft .NET Framework 3.5 on Windows Server 2012 | 2.0.50727.8987 AND 3.0.30729.8982 | KB5127660 | 2026-10-13 |
| Microsoft .NET Framework 3.5 on Windows Server 2012 R2 | 2.0.50727.8987 AND 3.0.30729.8982 | KB5127664 | 2026-10-13 |
| Microsoft .NET Framework 4.6.2/4.7/4.7.1/4.7.2 on Windows Server 2012 | 4.7.4150.0 | KB5127667 | 2026-10-13 |
| Microsoft .NET Framework 4.6.2/4.7/4.7.1/4.7.2 on Windows Server 2012 R2 | 4.7.4150.0 | KB5127668 | 2026-10-13 |
| Microsoft .NET Framework 4.8.1 on Windows 11 version 26H1 | 4.8.9363.0 | KB5127691 | 2026-10-13 |
| Microsoft .NET Framework 4.8 on Windows 10 version 1607 | 4.8.4811.0 | KB5127684 | 2026-10-13 |
| Microsoft .NET Framework 4.8 on Windows Server 2012 | 4.8.4811.0 | KB5127686 | 2026-10-13 |
| Microsoft .NET Framework 4.8 on Windows Server 2012 R2 | 4.8.4811.0 | KB5127688 | 2026-10-13 |
| Microsoft .NET Framework 4.8 on Windows Server 2016 | 4.8.4811.0 | KB5127684 | 2026-10-13 |
| System.Security.Cryptography.Pkcs on .NET 10.0 installed on Windows | 10.0.13 | configuration change | 2026-10-13 |
| System.Security.Cryptography.Pkcs on .NET 11.0 installed on Windows | 11.0.0-rc.2 | configuration change | 2026-10-13 |
| System.Security.Cryptography.Pkcs on .NET 8.0 installed on Windows | 8.0.2 | configuration change | 2026-10-13 |
| System.Security.Cryptography.Pkcs on .NET 9.0 installed on Windows | 9.0.21 | configuration change | 2026-10-13 |
Having the KB is not the same as knowing whether a machine has it. Windows updates supersede each other, so the update you installed often covers a fix that shipped in an earlier one. Paste your build into the patch checker and it walks that chain for you.
What it is
Inefficient algorithmic complexity in .NET allows an unauthorized attacker to deny service over a network.
Sources
CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H