--- id: "CVE-2026-70186" kind: "vulnerability" aliases: ["CVE-2026-70186", "GHSA-mf4x-w4gh-4656"] title: "Microsoft Security Advisory CVE-2026-70186 - ASP.NET Core Denial of Service Vulnerability" severity: "high" cvss: 7.5 epss: 0.008460000157356262 exploited: false status: "open" category: "runtime" products: [{"name": "Microsoft.AspNetCore.App.Runtime.linux-arm", "fixed": ["8.0.32"], "affected": ">= 8.0.0, <= 8.0.31", "ecosystem": "nuget"}, {"name": "Microsoft.AspNetCore.App.Runtime.linux-arm64", "fixed": ["8.0.32"], "affected": ">= 8.0.0, <= 8.0.31", "ecosystem": "nuget"}, {"name": "Microsoft.AspNetCore.App.Runtime.linux-musl-arm", "fixed": ["8.0.32"], "affected": ">= 8.0.0, <= 8.0.31", "ecosystem": "nuget"}, {"name": "Microsoft.AspNetCore.App.Runtime.linux-musl-arm64", "fixed": ["8.0.32"], "affected": ">= 8.0.0, <= 8.0.31", "ecosystem": "nuget"}, {"name": "Microsoft.AspNetCore.App.Runtime.linux-musl-x64", "fixed": ["8.0.32"], "affected": ">= 8.0.0, <= 8.0.31", "ecosystem": "nuget"}, {"name": "Microsoft.AspNetCore.App.Runtime.linux-x64", "fixed": ["8.0.32"], "affected": ">= 8.0.0, <= 8.0.31", "ecosystem": "nuget"}, {"name": "Microsoft.AspNetCore.App.Runtime.osx-arm64", "fixed": ["8.0.32"], "affected": ">= 8.0.0, <= 8.0.31", "ecosystem": "nuget"}, {"name": "Microsoft.AspNetCore.App.Runtime.osx-x64", "fixed": ["8.0.32"], "affected": ">= 8.0.0, <= 8.0.31", "ecosystem": "nuget"}, {"name": "Microsoft.AspNetCore.App.Runtime.win-arm64", "fixed": ["8.0.32"], "affected": ">= 8.0.0, <= 8.0.31", "ecosystem": "nuget"}, {"name": "Microsoft.AspNetCore.App.Runtime.win-x64", "fixed": ["8.0.32"], "affected": ">= 8.0.0, <= 8.0.31", "ecosystem": "nuget"}, {"name": "Microsoft.AspNetCore.App.Runtime.win-x86", "fixed": ["8.0.32"], "affected": ">= 8.0.0, <= 8.0.31", "ecosystem": "nuget"}, {"name": "Microsoft.AspNetCore.App.Runtime.linux-arm", "fixed": ["10.0.13"], "affected": ">= 10.0.0, <= 10.0.12", "ecosystem": "nuget"}, {"name": "Microsoft.AspNetCore.App.Runtime.linux-arm64", "fixed": ["10.0.13"], "affected": ">= 10.0.0, <= 10.0.12", "ecosystem": "nuget"}, {"name": "Microsoft.AspNetCore.App.Runtime.linux-musl-arm", "fixed": ["10.0.13"], "affected": ">= 10.0.0, <= 10.0.12", "ecosystem": "nuget"}, {"name": "Microsoft.AspNetCore.App.Runtime.linux-musl-arm64", "fixed": ["10.0.13"], "affected": ">= 10.0.0, <= 10.0.12", "ecosystem": "nuget"}, {"name": "Microsoft.AspNetCore.App.Runtime.linux-musl-x64", "fixed": ["10.0.13"], "affected": ">= 10.0.0, <= 10.0.12", "ecosystem": "nuget"}, {"name": "Microsoft.AspNetCore.App.Runtime.linux-x64", "fixed": ["10.0.13"], "affected": ">= 10.0.0, <= 10.0.12", "ecosystem": "nuget"}, {"name": "Microsoft.AspNetCore.App.Runtime.osx-arm64", "fixed": ["10.0.13"], "affected": ">= 10.0.0, <= 10.0.12", "ecosystem": "nuget"}, {"name": "Microsoft.AspNetCore.App.Runtime.osx-x64", "fixed": ["10.0.13"], "affected": ">= 10.0.0, <= 10.0.12", "ecosystem": "nuget"}, {"name": "Microsoft.AspNetCore.App.Runtime.win-arm64", "fixed": ["10.0.13"], "affected": ">= 10.0.0, <= 10.0.12", "ecosystem": "nuget"}, {"name": "Microsoft.AspNetCore.App.Runtime.win-x64", "fixed": ["10.0.13"], "affected": ">= 10.0.0, <= 10.0.12", "ecosystem": "nuget"}, {"name": "Microsoft.AspNetCore.App.Runtime.win-x86", "fixed": ["10.0.13"], "affected": ">= 10.0.0, <= 10.0.12", "ecosystem": "nuget"}, {"name": "Microsoft.AspNetCore.App.Runtime.linux-arm", "fixed": ["9.0.21"], "affected": ">= 9.0.0, <= 9.0.20", "ecosystem": "nuget"}, {"name": "Microsoft.AspNetCore.App.Runtime.linux-arm64", "fixed": ["9.0.21"], "affected": ">= 9.0.0, <= 9.0.20", "ecosystem": "nuget"}, {"name": "Microsoft.AspNetCore.App.Runtime.linux-musl-arm", "fixed": ["9.0.21"], "affected": ">= 9.0.0, <= 9.0.20", "ecosystem": "nuget"}, {"name": "Microsoft.AspNetCore.App.Runtime.linux-musl-arm64", "fixed": ["9.0.21"], "affected": ">= 9.0.0, <= 9.0.20", "ecosystem": "nuget"}, {"name": "Microsoft.AspNetCore.App.Runtime.linux-musl-x64", "fixed": ["9.0.21"], "affected": ">= 9.0.0, <= 9.0.20", "ecosystem": "nuget"}, {"name": "Microsoft.AspNetCore.App.Runtime.linux-x64", "fixed": ["9.0.21"], "affected": ">= 9.0.0, <= 9.0.20", "ecosystem": "nuget"}, {"name": "Microsoft.AspNetCore.App.Runtime.osx-arm64", "fixed": ["9.0.21"], "affected": ">= 9.0.0, <= 9.0.20", "ecosystem": "nuget"}, {"name": "Microsoft.AspNetCore.App.Runtime.osx-x64", "fixed": ["9.0.21"], "affected": ">= 9.0.0, <= 9.0.20", "ecosystem": "nuget"}, {"name": "Microsoft.AspNetCore.App.Runtime.win-arm64", "fixed": ["9.0.21"], "affected": ">= 9.0.0, <= 9.0.20", "ecosystem": "nuget"}, {"name": "Microsoft.AspNetCore.App.Runtime.win-x64", "fixed": ["9.0.21"], "affected": ">= 9.0.0, <= 9.0.20", "ecosystem": "nuget"}, {"name": "Microsoft.AspNetCore.App.Runtime.win-x86", "fixed": ["9.0.21"], "affected": ">= 9.0.0, <= 9.0.20", "ecosystem": "nuget"}] ecosystems: ["nuget"] tags: ["asp.net-core", "cwe-833", "dotnet", "http3", "kestrel", "linux", "macos", "runtime", "self-hosted", "windows"] not_affected_if: ["managed-hosting-patched", "no-http3-enabled", "not-on-affected-versions"] published_at: "2026-10-13T19:19:32+00:00" first_seen_at: "2026-10-23T19:11:32+00:00" updated_at: "2026-10-23T23:44:52+00:00" sources: [{"source": "ghsa", "url": "https://github.com/advisories/GHSA-mf4x-w4gh-4656", "first_seen_at": "2026-10-23T19:11:32+00:00"}, {"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-70186", "first_seen_at": "2026-10-23T23:44:52+00:00"}] --- # Microsoft Security Advisory CVE-2026-70186 - ASP.NET Core Denial of Service Vulnerability A flaw in ASP.NET Core's Kestrel server lets an unauthenticated remote attacker send crafted HTTP/3 reset or abort sequences that deadlock connection handling. Repeated requests make the server create excessive blocked threads, exhausting resources and causing denial of service. _Summary, check and fix written by a model from the sources; labelled as such._ ## Affected - nuget:Microsoft.AspNetCore.App.Runtime.linux-arm affected >= 8.0.0, <= 8.0.31 fixed 8.0.32 - nuget:Microsoft.AspNetCore.App.Runtime.linux-arm64 affected >= 8.0.0, <= 8.0.31 fixed 8.0.32 - nuget:Microsoft.AspNetCore.App.Runtime.linux-musl-arm affected >= 8.0.0, <= 8.0.31 fixed 8.0.32 - nuget:Microsoft.AspNetCore.App.Runtime.linux-musl-arm64 affected >= 8.0.0, <= 8.0.31 fixed 8.0.32 - nuget:Microsoft.AspNetCore.App.Runtime.linux-musl-x64 affected >= 8.0.0, <= 8.0.31 fixed 8.0.32 - nuget:Microsoft.AspNetCore.App.Runtime.linux-x64 affected >= 8.0.0, <= 8.0.31 fixed 8.0.32 - nuget:Microsoft.AspNetCore.App.Runtime.osx-arm64 affected >= 8.0.0, <= 8.0.31 fixed 8.0.32 - nuget:Microsoft.AspNetCore.App.Runtime.osx-x64 affected >= 8.0.0, <= 8.0.31 fixed 8.0.32 - nuget:Microsoft.AspNetCore.App.Runtime.win-arm64 affected >= 8.0.0, <= 8.0.31 fixed 8.0.32 - nuget:Microsoft.AspNetCore.App.Runtime.win-x64 affected >= 8.0.0, <= 8.0.31 fixed 8.0.32 - nuget:Microsoft.AspNetCore.App.Runtime.win-x86 affected >= 8.0.0, <= 8.0.31 fixed 8.0.32 - nuget:Microsoft.AspNetCore.App.Runtime.linux-arm affected >= 10.0.0, <= 10.0.12 fixed 10.0.13 - nuget:Microsoft.AspNetCore.App.Runtime.linux-arm64 affected >= 10.0.0, <= 10.0.12 fixed 10.0.13 - nuget:Microsoft.AspNetCore.App.Runtime.linux-musl-arm affected >= 10.0.0, <= 10.0.12 fixed 10.0.13 - nuget:Microsoft.AspNetCore.App.Runtime.linux-musl-arm64 affected >= 10.0.0, <= 10.0.12 fixed 10.0.13 - nuget:Microsoft.AspNetCore.App.Runtime.linux-musl-x64 affected >= 10.0.0, <= 10.0.12 fixed 10.0.13 - nuget:Microsoft.AspNetCore.App.Runtime.linux-x64 affected >= 10.0.0, <= 10.0.12 fixed 10.0.13 - nuget:Microsoft.AspNetCore.App.Runtime.osx-arm64 affected >= 10.0.0, <= 10.0.12 fixed 10.0.13 - nuget:Microsoft.AspNetCore.App.Runtime.osx-x64 affected >= 10.0.0, <= 10.0.12 fixed 10.0.13 - nuget:Microsoft.AspNetCore.App.Runtime.win-arm64 affected >= 10.0.0, <= 10.0.12 fixed 10.0.13 - nuget:Microsoft.AspNetCore.App.Runtime.win-x64 affected >= 10.0.0, <= 10.0.12 fixed 10.0.13 - nuget:Microsoft.AspNetCore.App.Runtime.win-x86 affected >= 10.0.0, <= 10.0.12 fixed 10.0.13 - nuget:Microsoft.AspNetCore.App.Runtime.linux-arm affected >= 9.0.0, <= 9.0.20 fixed 9.0.21 - nuget:Microsoft.AspNetCore.App.Runtime.linux-arm64 affected >= 9.0.0, <= 9.0.20 fixed 9.0.21 - nuget:Microsoft.AspNetCore.App.Runtime.linux-musl-arm affected >= 9.0.0, <= 9.0.20 fixed 9.0.21 - nuget:Microsoft.AspNetCore.App.Runtime.linux-musl-arm64 affected >= 9.0.0, <= 9.0.20 fixed 9.0.21 - nuget:Microsoft.AspNetCore.App.Runtime.linux-musl-x64 affected >= 9.0.0, <= 9.0.20 fixed 9.0.21 - nuget:Microsoft.AspNetCore.App.Runtime.linux-x64 affected >= 9.0.0, <= 9.0.20 fixed 9.0.21 - nuget:Microsoft.AspNetCore.App.Runtime.osx-arm64 affected >= 9.0.0, <= 9.0.20 fixed 9.0.21 - nuget:Microsoft.AspNetCore.App.Runtime.osx-x64 affected >= 9.0.0, <= 9.0.20 fixed 9.0.21 - nuget:Microsoft.AspNetCore.App.Runtime.win-arm64 affected >= 9.0.0, <= 9.0.20 fixed 9.0.21 - nuget:Microsoft.AspNetCore.App.Runtime.win-x64 affected >= 9.0.0, <= 9.0.20 fixed 9.0.21 - nuget:Microsoft.AspNetCore.App.Runtime.win-x86 affected >= 9.0.0, <= 9.0.20 fixed 9.0.21 ## How to check Run dotnet --info to list installed .NET runtime versions; check whether any 8.0 runtime is 8.0.31 or lower, or any 9.0 runtime is 9.0.20 or lower, or any 10.0 runtime is 10.0.12 or lower. Check your project files for Microsoft.AspNetCore.App.Runtime.* package references at those versions. ## Fix Install the latest .NET runtime and restart apps: 8.0.32 or later for 8.x, 9.0.21 or later for 9.x, 10.0.13 or later for 10.x. Recompile and redeploy self-contained apps built against affected versions. ## Timeline - 2026-10-23T19:11:32+00:00 ghsa https://github.com/advisories/GHSA-mf4x-w4gh-4656 - 2026-10-23T23:44:52+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-70186 ## From the sources ## 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:** `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H` - **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, <= 8.0.31 | 8.0.32 [Microsoft.AspNetCore.App.Runtime.linux-arm64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.linux-arm64) | >= 8.0.0, <= 8.0.31 | 8.0.32 [Microsoft.AspNetCore.App.Runtime.linux-musl-arm](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.linux-musl-arm) | >= 8.0.0, <= 8.0.31 | 8.0.32 [Microsoft.AspNetCore.App.Runtime.linux-musl-arm64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.linux-musl-arm64) | >= 8.0.0, <= 8.0.31 | 8.0.32 [Microsoft.AspNetCore.App.Runtime.linux-musl-x64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.linux-musl-x64) | >= 8.0.0, <= 8.0.31 | 8.0.32 [Microsoft.AspNetCore.App.Runtime.linux-x64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.linux-x64) | >= 8.0.0, <= 8.0.31 | 8.0.32 [Microsoft.AspNetCore.App.Runtime.osx-arm64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.osx-arm64) | >= 8.0.0, <= 8.0.31 | 8.0.32 [Microsoft.AspNetCore.App.Runtime.osx-x64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.osx-x64) | >= 8.0.0, <= 8.0.31 | 8.0.32 [Microsoft.AspNetCore.App.Runtime.win-arm](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.win-arm) | >= 8.0.0, <= 8.0.31 | 8.0.32 [Microsoft.AspNetCore.App.Runtime.win-arm64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.win-arm64) | >= 8.0.0, <= 8.0.31 | 8.0.32 [Microsoft.AspNetCore.App.Runtime.win-x64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.win-x64) | >= 8.0.0, <= 8.0.31 | 8.0.32 [Microsoft.AspNetCore.App.Runtime.win-x86](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.win-x86) | >= 8.0.0, <= 8.0.31 | 8.0.32 [Microsoft.AspNetCore.App.Runtime.linux-arm](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.linux-arm) | >= 10.0.0, <= 10.0.12 | 10.0.13 [Microsoft.AspNetCore.App.Runtime.linux-arm64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.linux-arm64) | >= 10.0.0, <= 10.0.12 | 10.0.13 [Microsoft.AspNetCore.App.Runtime.linux-musl-arm](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.linux-musl-arm) | >= 10.0.0, <= 10.0.12 | 10.0.13 [Microsoft.AspNetCore.App.Runtime.linux-musl-arm64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.linux-musl-arm64) | >= 10.0.0, <= 10.0.12 | 10.0.13 [Microsoft.AspNetCore.App.Runtime.linux-musl-x64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.linux-musl-x64) | >= 10.0.0, <= 10.0.12 | 10.0.13 [Microsoft.AspNetCore.App.Runtime.linux-x64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.linux-x64) | >= 10.0.0, <= 10.0.12 | 10.0.13 [Microsoft.AspNetCore.App.Runtime.osx-arm64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.osx-arm64) | >= 10.0.0, <= 10.0.12 | 10.0.13 [Microsoft.AspNetCore.App.Runtime.osx-x64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.osx-x64) | >= 10.0.0, <= 10.0.12 | 10.0.13 [Microsoft.AspNetCore.App.Runtime.win-arm](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.win-arm) | >= 10.0.0, <= 10.0.12 | 10.0.13 [Microsoft.AspNetCore.App.Runtime.win-arm64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.win-arm64) | >= 10.0.0, <= 10.0.12 | 10.0.13 [Microsoft.AspNetCore.App.Runtime.win-x64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.win-x64) | >= 10.0.0, <= 10.0.12 | 10.0.13 [Microsoft.AspNetCore.App.Runtime.win-x86](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.win-x86) | >= 10.0.0, <= 10.0.12 | 10.0.13 [Microsoft.AspNetCore.App.Runtime.linux-arm](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.linux-arm) | >= 9.0.0, <= 9.0.20 | 9.0.21 [Microsoft.AspNetCore.App.Runtime.linux-arm64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.linux-arm64) | >= 9.0.0, <= 9.0.20 | 9.0.21 [Microsoft.AspNetCore.App.Runtime.linux-musl-arm](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.linux-musl-arm) | >= 9.0.0, <= 9.0.20 | 9.0.21 [Microsoft.AspNetCore.App.Runtime.linux-musl-arm64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.linux-musl-arm64) | >= 9.0.0, <= 9.0.20 | 9.0.21 [Microsoft.AspNetCore.App.Runtime.linux-musl-x64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.linux-musl-x64) | >= 9.0.0, <= 9.0.20 | 9.0.21 [Microsoft.AspNetCore.App.Runtime.linux-x64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.linux-x64) | >= 9.0.0, <= 9.0.20 | 9.0.21 [Microsoft.AspNetCore.App.Runtime.osx-arm64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.osx-arm64) | >= 9.0.0, <= 9.0.20 | 9.0.21 [Microsoft.AspNetCore.App.Runtime.osx-x64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.osx-x64) | >= 9.0.0, <= 9.0.20 | 9.0.21 [Microsoft.AspNetCore.App.Runtime.win-arm](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.win-arm) | >= 9.0.0, <= 9.0.20 | 9.0.21 [Microsoft.AspNetCore.App.Runtime.win-arm64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.win-arm64) | >= 9.0.0, <= 9.0.20 | 9.0.21 [Microsoft.AspNetCore.App.Runtime.win-x64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.win-x64) | >= 9.0.0, <= 9.0.20 | 9.0.21 [Microsoft.AspNetCore.App.Runtime.win-x86](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.win-x86) | >= 9.0.0, <= 9.0.20 | 9.0.21 ## Advisory FAQ ### 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, update the package reference to the patched version. You can list the versions you have installed by running the `dotnet --info` command. Once you have installed the updated runtime or SDK, restart your apps for the update to take effect. Additionally, if you've deployed [self-contained applications](https://docs.microsoft.com/dotnet/core/deploying/#self-contained-deployments-scd) targeting any of the impacted versions, these applications are also vulnerable and must be recompiled and redeployed. ## Other Information ### Reporting Security Issues If you have found a potential security issue in a supported version of .NET, please report it to the Microsoft Security Response Center (MSRC) via the [MSRC Researcher Portal](https://msrc.microsoft.c --- _Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_