# CVE-2026-70186: ASP.NET Core Kestrel denial of service in HTTP/3 handling

Source: https://junglewise.ai/threats/cve-2026-70186-microsoft-security-advisory-asp-net-core-denial-of-service  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-13. Updated: 2026-10-13  
License: CC BY 4.0 with a link back

CVE-2026-70186 · Severity: high · CVSS 7.5 · Published 2026-10-13

Microsoft ASP.NET Core's Kestrel web server can be crashed by unauthenticated attackers who send specially crafted HTTP/3 reset or abort messages. Repeated requests cause the server to deadlock and exhaust resources, resulting in service unavailability for legitimate users.

Technologies: [Microsoft Asp.Net Core](https://junglewise.ai/threats/technologies/asp-net-core), [Microsoft.AspNetCore.App.Runtime.linux-arm (NuGet)](https://junglewise.ai/threats/technologies/microsoft-aspnetcore-app-runtime-linux-arm), [Microsoft.AspNetCore.App.Runtime.linux-arm64 (NuGet)](https://junglewise.ai/threats/technologies/microsoft-aspnetcore-app-runtime-linux-arm64), [Microsoft.AspNetCore.App.Runtime.linux-musl-arm (NuGet)](https://junglewise.ai/threats/technologies/microsoft-aspnetcore-app-runtime-linux-musl-arm), [Microsoft.AspNetCore.App.Runtime.linux-musl-arm64 (NuGet)](https://junglewise.ai/threats/technologies/microsoft-aspnetcore-app-runtime-linux-musl-arm64), [Microsoft.AspNetCore.App.Runtime.linux-musl-x64 (NuGet)](https://junglewise.ai/threats/technologies/microsoft-aspnetcore-app-runtime-linux-musl-x64), [Microsoft.AspNetCore.App.Runtime.linux-x64 (NuGet)](https://junglewise.ai/threats/technologies/microsoft-aspnetcore-app-runtime-linux-x64), [Microsoft.AspNetCore.App.Runtime.osx-arm64 (NuGet)](https://junglewise.ai/threats/technologies/microsoft-aspnetcore-app-runtime-osx-arm64), [Microsoft.AspNetCore.App.Runtime.osx-x64 (NuGet)](https://junglewise.ai/threats/technologies/microsoft-aspnetcore-app-runtime-osx-x64), [Microsoft.AspNetCore.App.Runtime.win-arm64 (NuGet)](https://junglewise.ai/threats/technologies/microsoft-aspnetcore-app-runtime-win-arm64), [Microsoft.AspNetCore.App.Runtime.win-x64 (NuGet)](https://junglewise.ai/threats/technologies/microsoft-aspnetcore-app-runtime-win-x64), [Microsoft.AspNetCore.App.Runtime.win-x86 (NuGet)](https://junglewise.ai/threats/technologies/microsoft-aspnetcore-app-runtime-win-x86). Vendors: [Microsoft](https://junglewise.ai/threats/vendors/microsoft), [NuGet](https://junglewise.ai/threats/vendors/nuget).

## Quick answers

**Is CVE-2026-70186 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-70186 being exploited in the wild.

**How severe is CVE-2026-70186?** High severity, with a CVSS score of 7.5, published 13 October 2026.

**Which products and versions are affected?** Microsoft Asp.Net Core 8.0.0 to 8.0.31, 9.0.0 to 9.0.20, 10.0.0 to 10.0.12; Microsoft.AspNetCore.App.Runtime.linux-arm (NuGet) >= 8.0.0, <= 8.0.31, ECOSYSTEM:introduced=8.0.0,fixed=8.0.32; Microsoft.AspNetCore.App.Runtime.linux-arm64 (NuGet) >= 8.0.0, <= 8.0.31, ECOSYSTEM:introduced=8.0.0,fixed=8.0.32; Microsoft.AspNetCore.App.Runtime.linux-musl-arm (NuGet) >= 8.0.0, <= 8.0.31, ECOSYSTEM:introduced=8.0.0,fixed=8.0.32; and 8 more.

**Is there a fix for CVE-2026-70186?** Yes. Microsoft.AspNetCore.App.Runtime.linux-arm (NuGet): upgrade to 8.0.32 or later; Microsoft.AspNetCore.App.Runtime.linux-arm64 (NuGet): upgrade to 8.0.32 or later; Microsoft.AspNetCore.App.Runtime.linux-musl-arm (NuGet): upgrade to 8.0.32 or later; Microsoft.AspNetCore.App.Runtime.linux-musl-arm64 (NuGet): upgrade to 8.0.32 or later; Microsoft.AspNetCore.App.Runtime.linux-musl-x64 (NuGet): upgrade to 8.0.32 or later; Microsoft.AspNetCore.App.Runtime.linux-x64 (NuGet): upgrade to 8.0.32 or later; Microsoft.AspNetCore.App.Runtime.osx-arm64 (NuGet): upgrade to 8.0.32 or later; Microsoft.AspNetCore.App.Runtime.osx-x64 (NuGet): upgrade to 8.0.32 or later; Microsoft.AspNetCore.App.Runtime.win-arm64 (NuGet): upgrade to 8.0.32 or later; Microsoft.AspNetCore.App.Runtime.win-x64 (NuGet): upgrade to 8.0.32 or later; Microsoft.AspNetCore.App.Runtime.win-x86 (NuGet): upgrade to 8.0.32 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-70186 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-70186?** Check whether you run Microsoft Asp.Net Core, Microsoft.AspNetCore.App.Runtime.linux-arm (NuGet), Microsoft.AspNetCore.App.Runtime.linux-arm64 (NuGet) or one of the others listed at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- Microsoft.AspNetCore.App.Runtime.linux-arm (NuGet): upgrade to 8.0.32 or later

  ```sh
  dotnet add package Microsoft.AspNetCore.App.Runtime.linux-arm --version 8.0.32
  ```

- Microsoft.AspNetCore.App.Runtime.linux-arm64 (NuGet): upgrade to 8.0.32 or later

  ```sh
  dotnet add package Microsoft.AspNetCore.App.Runtime.linux-arm64 --version 8.0.32
  ```

- Microsoft.AspNetCore.App.Runtime.linux-musl-arm (NuGet): upgrade to 8.0.32 or later

  ```sh
  dotnet add package Microsoft.AspNetCore.App.Runtime.linux-musl-arm --version 8.0.32
  ```

- Microsoft.AspNetCore.App.Runtime.linux-musl-arm64 (NuGet): upgrade to 8.0.32 or later

  ```sh
  dotnet add package Microsoft.AspNetCore.App.Runtime.linux-musl-arm64 --version 8.0.32
  ```

- Microsoft.AspNetCore.App.Runtime.linux-musl-x64 (NuGet): upgrade to 8.0.32 or later

  ```sh
  dotnet add package Microsoft.AspNetCore.App.Runtime.linux-musl-x64 --version 8.0.32
  ```

- Microsoft.AspNetCore.App.Runtime.linux-x64 (NuGet): upgrade to 8.0.32 or later

  ```sh
  dotnet add package Microsoft.AspNetCore.App.Runtime.linux-x64 --version 8.0.32
  ```

- Microsoft.AspNetCore.App.Runtime.osx-arm64 (NuGet): upgrade to 8.0.32 or later

  ```sh
  dotnet add package Microsoft.AspNetCore.App.Runtime.osx-arm64 --version 8.0.32
  ```

- Microsoft.AspNetCore.App.Runtime.osx-x64 (NuGet): upgrade to 8.0.32 or later

  ```sh
  dotnet add package Microsoft.AspNetCore.App.Runtime.osx-x64 --version 8.0.32
  ```

- Microsoft.AspNetCore.App.Runtime.win-arm64 (NuGet): upgrade to 8.0.32 or later

  ```sh
  dotnet add package Microsoft.AspNetCore.App.Runtime.win-arm64 --version 8.0.32
  ```

- Microsoft.AspNetCore.App.Runtime.win-x64 (NuGet): upgrade to 8.0.32 or later

  ```sh
  dotnet add package Microsoft.AspNetCore.App.Runtime.win-x64 --version 8.0.32
  ```

- Microsoft.AspNetCore.App.Runtime.win-x86 (NuGet): upgrade to 8.0.32 or later

  ```sh
  dotnet add package Microsoft.AspNetCore.App.Runtime.win-x86 --version 8.0.32
  ```


## Technical details

The vulnerability is a deadlock condition (CWE-833) in Microsoft.AspNetCore.Server.Kestrel.Core's HTTP/3 connection handling. An unauthenticated remote attacker can exploit this via network access by sending malformed HTTP/3 reset or abort sequences, causing excessive blocked-thread creation that exhausts server resources. The issue affects HTTP/3-enabled Kestrel instances on .NET 8, 9, and 10.

## Affected products

- Microsoft ASP.NET Core 8.0.0 to 8.0.31, 9.0.0 to 9.0.20, 10.0.0 to 10.0.12

## Identifiers

- CVE-2026-70186
- GHSA-mf4x-w4gh-4656

## Timeline

- 2026-10-13: advisory

## Related threats

- [Microsoft ASP.NET Core resource exhaustion denial of service](https://junglewise.ai/threats/cve-2026-109468-allocation-of-resources-without-limits-or-throttling-in-asp-net)
- [Microsoft ASP.NET Core Kestrel HTTP request smuggling in HTTP/2](https://junglewise.ai/threats/cve-2026-70188-microsoft-security-advisory-asp-net-core-security-feature-bypass)
- [Microsoft ASP.NET Core Localization denial of service](https://junglewise.ai/threats/cve-2026-96236-microsoft-security-advisory-asp-net-core-denial-of-service)
- [Microsoft ASP.NET Core authorization bypass in Blazor AuthorizeRouteView](https://junglewise.ai/threats/cve-2026-70183-microsoft-security-advisory-asp-net-core-security-feature-bypass)
- [ASP.NET Core denial of service in FormPipeReader](https://junglewise.ai/threats/cve-2026-70196-microsoft-security-advisory-asp-net-core-denial-of-service)