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CVE-2026-70186

Microsoft Security Advisory CVE-2026-70186 - ASP.NET Core Denial of Service Vulnerability

Published Oct 13, 2026 · updated Oct 13, 2026 · Microsoft ASP.NET Core 10.0

## Executive summary Microsoft is releasing this security advisory to provide information about a vulnerability in Microsoft.AspNetCore.Server.Kestrel.Core. This advisory also provides guidance on what developers can do to update their applications to remove this vulnerability. An unauthenticated remote attacker can send crafted HTTP/3 reset or abort sequences that deadlock Kestrel connection handling. Repeated requests can cause excessive blocked-thread creation and exhaust server resources, resulting in denial of service. ## Announcement Announcement for this issue can be found at https://github.com/dotnet/announcements/issues/461 ## CVSS Details - **Version:** 3.1 - **Severity:** High - **Score:** 7.5 - **Vector:** - **Weakness:** CWE-833 (Deadlock) ## Affected Platforms - **Platforms:** Windows, Linux, macOS with HTTP/3 support - **Architectures:** All ## Affected Packages The vulnerability affects Microsoft .NET projects that use an affected package version listed below. Package name | Affected version | Patched version ------------ | ---------------- | --------------- [Microsoft.AspNetCore.App.Runtime.linux-arm](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.linux-arm) | >= 8.0.0, = 8.0.0, = 8.0.0, = 8.0.0, = 8.0.0, = 8.0.0, = 8.0.0, = 8.0.0, = 8.0.0, = 8.0.0, = 8.0.0, = 8.0.0, = 10.0.0, = 10.0.0, = 10.0.0, = 10.0.0, = 10.0.0, = 10.0.0, = 10.0.0, = 10.0.0, = 10.0.0, = 10.0.0, = 10.0.0, = 10.0.0, = 9.0.0, = 9.0.0, = 9.0.0, = 9.0.0, = 9.0.0, = 9.0.0, = 9.0.0, = 9.0.0, = 9.0.0, = 9.0.0, = 9.0.0, = 9.0.0, How do I know if I am affected? If using a package listed in [affected packages](#affected-packages), you're exposed to the vulnerability. ### How do I fix the issue? 1. To fix the issue please install the latest version of .NET. If you have installed one or more .NET SDKs through Visual Studio, Visual Studio will prompt you to update Visual Studio, which will also update your .NET SDKs. 2. If your application references the vulnerable package, u

Timeline

Detection, updates, and resolution for this record.

  1. Oct 13, 2026 · Catalog

    Detected

    ## Executive summary Microsoft is releasing this security advisory to provide information about a vulnerability in Microsoft.AspNetCore.Server.Kestrel.Core. This advisory also provides guidance on what developers can do to update their applications to remove this vulnerability. An unauthenticated remote attacker can send crafted HTTP/3 reset or abort sequences that deadlock Kestrel connection hand

  2. Oct 13, 2026 · Catalog

    Fix available

    NuGet Microsoft.AspNetCore.App.Runtime.linux-arm 8.0.0 → 8.0.32

  3. Oct 13, 2026 · Catalog

    Fix available

    NuGet Microsoft.AspNetCore.App.Runtime.linux-arm64 8.0.0 → 8.0.32

  4. Oct 13, 2026 · Catalog

    Fix available

    NuGet Microsoft.AspNetCore.App.Runtime.linux-musl-arm 8.0.0 → 8.0.32

  5. Oct 13, 2026 · Catalog

    Fix available

    NuGet Microsoft.AspNetCore.App.Runtime.linux-musl-arm64 8.0.0 → 8.0.32

  6. Oct 13, 2026 · Catalog

    Fix available

    NuGet Microsoft.AspNetCore.App.Runtime.linux-musl-x64 8.0.0 → 8.0.32

  7. Oct 13, 2026 · Catalog

    Fix available

    NuGet Microsoft.AspNetCore.App.Runtime.linux-x64 8.0.0 → 8.0.32

  8. Oct 13, 2026 · Catalog

    Fix available

    NuGet Microsoft.AspNetCore.App.Runtime.osx-arm64 8.0.0 → 8.0.32

  9. Oct 13, 2026 · Catalog

    Fix available

    NuGet Microsoft.AspNetCore.App.Runtime.osx-x64 8.0.0 → 8.0.32

  10. Oct 13, 2026 · Catalog

    Fix available

    NuGet Microsoft.AspNetCore.App.Runtime.win-arm64 8.0.0 → 8.0.32

  11. Oct 13, 2026 · Catalog

    Fix available

    NuGet Microsoft.AspNetCore.App.Runtime.win-x64 8.0.0 → 8.0.32

  12. Oct 13, 2026 · Catalog

    Fix available

    NuGet Microsoft.AspNetCore.App.Runtime.win-x86 8.0.0 → 8.0.32

  13. Oct 13, 2026 · Catalog

    Fix available

    NuGet Microsoft.AspNetCore.App.Runtime.linux-arm 10.0.0 → 10.0.13

  14. Oct 13, 2026 · Catalog

    Updated

    ## Executive summary Microsoft is releasing this security advisory to provide information about a vulnerability in Microsoft.AspNetCore.Server.Kestrel.Core. This advisory also provides guidance on what developers can do to update their applications to remove this vulnerability. An unauthenticated remote attacker can send crafted HTTP/3 reset or abort sequences that deadlock Kestrel connection hand

Affected

  • NuGet Microsoft.AspNetCore.App.Runtime.linux-arm10.0.0 → 10.0.13
  • NuGet Microsoft.AspNetCore.App.Runtime.linux-arm8.0.0 → 8.0.32
  • NuGet Microsoft.AspNetCore.App.Runtime.linux-arm648.0.0 → 8.0.32
  • NuGet Microsoft.AspNetCore.App.Runtime.linux-musl-arm8.0.0 → 8.0.32
  • NuGet Microsoft.AspNetCore.App.Runtime.linux-musl-arm648.0.0 → 8.0.32
  • NuGet Microsoft.AspNetCore.App.Runtime.linux-musl-x648.0.0 → 8.0.32
  • NuGet Microsoft.AspNetCore.App.Runtime.linux-x648.0.0 → 8.0.32
  • NuGet Microsoft.AspNetCore.App.Runtime.osx-arm648.0.0 → 8.0.32
  • NuGet Microsoft.AspNetCore.App.Runtime.osx-x648.0.0 → 8.0.32
  • NuGet Microsoft.AspNetCore.App.Runtime.win-arm648.0.0 → 8.0.32
  • NuGet Microsoft.AspNetCore.App.Runtime.win-x648.0.0 → 8.0.32
  • NuGet Microsoft.AspNetCore.App.Runtime.win-x868.0.0 → 8.0.32
  • vendor Microsoft ASP.NET Core 10.0version unspecified

Sources

  • CVE.orgCVE-2026-70186

    Deadlock in ASP.NET Core allows an unauthorized attacker to deny service over a network.

    cve.org
  • GitHub Advisory DatabaseGHSA-mf4x-w4gh-4656

    GitHub Advisory Database record mirrored by OSV.

    github.com
  • OSV.devGHSA-mf4x-w4gh-4656

    Microsoft Security Advisory CVE-2026-70186 - ASP.NET Core Denial of Service Vulnerability

    osv.dev

References