{"id":"CVE-2026-70188","kind":"vulnerability","aliases":["CVE-2026-70188","GHSA-fpq8-4vhr-rcxx"],"related":[],"title":"Microsoft Security Advisory CVE-2026-70188 - ASP.NET Core Security Feature Bypass Vulnerability","description":"## Executive summary\n\nMicrosoft 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.\n\nKestrel accepts newline characters in HTTP/2 request trailers and values retrieved from the dynamic HPACK table instead of treating them as malformed.\n\n## Announcement\n\nAnnouncement for this issue can be found at https://github.com/dotnet/announcements/issues/462\n\n## CVSS Details\n\n- **Version:** 3.1\n- **Severity:** Critical\n- **Score:** 9.1\n- **Vector:** `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N`\n- **Weakness:** CWE-444 (Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling'))\n\n## Affected Platforms\n\n- **Platforms:** Windows, Linux, macOS\n- **Architectures:** All\n\n## <a name=\"affected-packages\"></a>Affected Packages\n\nThe vulnerability affects Microsoft .NET projects that use an affected package version listed below.\n\nPackage name | Affected version | Patched version\n------------ | ---------------- | ---------------\n[Microsoft.AspNetCore.App.Runtime.linux-arm](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.linux-arm) | >= 11.0.0-preview.1, <= 11.0.0-rc.1 | 11.0.0-rc.2\n[Microsoft.AspNetCore.App.Runtime.linux-arm64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.linux-arm64) | >= 11.0.0-preview.1, <= 11.0.0-rc.1 | 11.0.0-rc.2\n[Microsoft.AspNetCore.App.Runtime.linux-musl-arm](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.linux-musl-arm) | >= 11.0.0-preview.1, <= 11.0.0-rc.1 | 11.0.0-rc.2\n[Microsoft.AspNetCore.App.Runtime.linux-musl-arm64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.linux-musl-arm64) | >= 11.0.0-preview.1, <= 11.0.0-rc.1 | 11.0.0-rc.2\n[Microsoft.AspNetCore.App.Runtime.linux-musl-x64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.linux-musl-x64) | >= 11.0.0-preview.1, <= 11.0.0-rc.1 | 11.0.0-rc.2\n[Microsoft.AspNetCore.App.Runtime.linux-x64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.linux-x64) | >= 11.0.0-preview.1, <= 11.0.0-rc.1 | 11.0.0-rc.2\n[Microsoft.AspNetCore.App.Runtime.osx-arm64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.osx-arm64) | >= 11.0.0-preview.1, <= 11.0.0-rc.1 | 11.0.0-rc.2\n[Microsoft.AspNetCore.App.Runtime.osx-x64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.osx-x64) | >= 11.0.0-preview.1, <= 11.0.0-rc.1 | 11.0.0-rc.2\n[Microsoft.AspNetCore.App.Runtime.win-arm](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.win-arm) | >= 11.0.0-preview.1, <= 11.0.0-rc.1 | 11.0.0-rc.2\n[Microsoft.AspNetCore.App.Runtime.win-arm64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.win-arm64) | >= 11.0.0-preview.1, <= 11.0.0-rc.1 | 11.0.0-rc.2\n[Microsoft.AspNetCore.App.Runtime.win-x64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.win-x64) | >= 11.0.0-preview.1, <= 11.0.0-rc.1 | 11.0.0-rc.2\n[Microsoft.AspNetCore.App.Runtime.win-x86](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.win-x86) | >= 11.0.0-preview.1, <= 11.0.0-rc.1 | 11.0.0-rc.2\n[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\n[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\n[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\n[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\n[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\n[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\n[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\n[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\n[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\n[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\n[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\n[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\n[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\n[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\n[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\n[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\n[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\n[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\n[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\n[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\n[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\n[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\n[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\n[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\n[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\n[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\n[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\n[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\n[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\n[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\n[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\n[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\n[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\n[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\n[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\n[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\n\n## Advisory FAQ\n\n### <a name=\"how-affected\"></a>How do I know if I am affected?\n\nIf using a package listed in [affected packages](#affected-packages), you're exposed to the vulnerability.\n\n### <a name=\"how-fix\"></a>How do I fix the issue?\n\n1. 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.\n2. 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.\n\nOnce you have installed the updated runtime or SDK, restart your apps for the update to take effect.\n\nAdditionally, 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.\n\n## Other Information\n\n### Reporting Security Issues\n\nIf 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.com/report/vulnerability/new). Further information can be found in the MSRC [Report an Issue FAQ](https://www.microsoft.com/msrc/faqs-report-an-issue).\n\nSecurity reports made through MSRC may qualify for the Microsoft .NET Bounty. Details of the Microsoft .NET Bounty Program including terms and conditions are at https://aka.ms/corebounty.\n\n### Support\n\nYou can ask questions about this issue on GitHub in the .NET GitHub organization. The main repos are located at https://github.com/dotnet/runtime. The Announcements repo (https://github.com/dotnet/Announcements) will contain this bulletin as an issue and will include a link to a discussion issue. You can ask questions in the linked discussion issue.\n\n### Disclaimer\n\nThe information provided in this advisory is provided \"as is\" without warranty of any kind. Microsoft disclaims all warranties, either express or implied, including the warranties of merchantability and fitness for a particular purpose. In no event shall Microsoft Corporation or its suppliers be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages, even if Microsoft Corporation or its suppliers have been advised of the possibility of such damages. Some states do not allow the exclusion or limitation of liability for consequential or incidental damages so the foregoing limitation may not apply.\n\n### External Links\n\n[CVE-2026-70188](https://www.cve.org/CVERecord?id=CVE-2026-70188)\n\n### Acknowledgements\n\n- Aayush Atharva\n\n### Revisions\n\nV1.0 (10/13/2026): Advisory published.","summary":"ASP.NET Core's Kestrel HTTP server accepts newline characters in HTTP/2 request trailers and HPACK dynamic-table values instead of rejecting them as malformed, enabling HTTP request smuggling (CWE-444). An unauthenticated remote attacker can use this to desynchronize request handling and gain high confidentiality and integrity impact.","severity":"critical","cvss":9.100000381469727,"epss":0.008270000107586384,"exploited":false,"exploited_at":null,"products":[{"name":"Microsoft.AspNetCore.App.Runtime.linux-arm","fixed":["11.0.0-rc.2"],"affected":">= 11.0.0-preview.1, <= 11.0.0-rc.1","ecosystem":"nuget"},{"name":"Microsoft.AspNetCore.App.Runtime.linux-arm64","fixed":["11.0.0-rc.2"],"affected":">= 11.0.0-preview.1, <= 11.0.0-rc.1","ecosystem":"nuget"},{"name":"Microsoft.AspNetCore.App.Runtime.linux-musl-arm","fixed":["11.0.0-rc.2"],"affected":">= 11.0.0-preview.1, <= 11.0.0-rc.1","ecosystem":"nuget"},{"name":"Microsoft.AspNetCore.App.Runtime.linux-musl-arm64","fixed":["11.0.0-rc.2"],"affected":">= 11.0.0-preview.1, <= 11.0.0-rc.1","ecosystem":"nuget"},{"name":"Microsoft.AspNetCore.App.Runtime.linux-musl-x64","fixed":["11.0.0-rc.2"],"affected":">= 11.0.0-preview.1, <= 11.0.0-rc.1","ecosystem":"nuget"},{"name":"Microsoft.AspNetCore.App.Runtime.linux-x64","fixed":["11.0.0-rc.2"],"affected":">= 11.0.0-preview.1, <= 11.0.0-rc.1","ecosystem":"nuget"},{"name":"Microsoft.AspNetCore.App.Runtime.osx-arm64","fixed":["11.0.0-rc.2"],"affected":">= 11.0.0-preview.1, <= 11.0.0-rc.1","ecosystem":"nuget"},{"name":"Microsoft.AspNetCore.App.Runtime.osx-x64","fixed":["11.0.0-rc.2"],"affected":">= 11.0.0-preview.1, <= 11.0.0-rc.1","ecosystem":"nuget"},{"name":"Microsoft.AspNetCore.App.Runtime.win-arm64","fixed":["11.0.0-rc.2"],"affected":">= 11.0.0-preview.1, <= 11.0.0-rc.1","ecosystem":"nuget"},{"name":"Microsoft.AspNetCore.App.Runtime.win-x64","fixed":["11.0.0-rc.2"],"affected":">= 11.0.0-preview.1, <= 11.0.0-rc.1","ecosystem":"nuget"},{"name":"Microsoft.AspNetCore.App.Runtime.win-x86","fixed":["11.0.0-rc.2"],"affected":">= 11.0.0-preview.1, <= 11.0.0-rc.1","ecosystem":"nuget"},{"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-444","dotnet","http2","kestrel","runtime","self-hosted"],"not_affected_if":["default-config","managed-hosting","non-http2-only-deployments"],"how_to_check":"Run dotnet --list-runtimes and dotnet --info to see installed runtime versions; compare the Microsoft.AspNetCore.App.Runtime.* package versions in your projects against the affected ranges.\nCheck project files and packages.lock.json for Microsoft.AspNetCore.App.Runtime.* references at 11.0.0-preview.1 through 11.0.0-rc.1, 10.0.0 through 10.0.12, 9.0.0 through 9.0.20, or 8.0.0 through 8.0.31.","fix":"Update to the patched runtime: 11.0.0-rc.2, 10.0.13, 9.0.21, or 8.0.32, and install the latest .NET; recompile and redeploy self-contained apps and restart services after updating.\nFor the 8.0 line, the advisory lists 8.0.32 as the fix; note the 8.0 range is listed on the affected rows only for linux-arm in the source table.","status":"open","published_at":"2026-10-13T19:19:33+00:00","first_seen_at":"2026-10-23T19:11:32+00:00","triaged_at":"2026-10-23T19:51:08+00:00","updated_at":"2026-10-23T23:44:52+00:00","category":"runtime","confidence":0.8,"triage":{"at":"2026-10-23T19:51:08Z","model":"claude-haiku-5-5","output":{"fix":"Update to the patched runtime: 11.0.0-rc.2, 10.0.13, 9.0.21, or 8.0.32, and install the latest .NET; recompile and redeploy self-contained apps and restart services after updating.\nFor the 8.0 line, the advisory lists 8.0.32 as the fix; note the 8.0 range is listed on the affected rows only for linux-arm in the source table.","summary":"ASP.NET Core's Kestrel HTTP server accepts newline characters in HTTP/2 request trailers and HPACK dynamic-table values instead of rejecting them as malformed, enabling HTTP request smuggling (CWE-444). An unauthenticated remote attacker can use this to desynchronize request handling and gain high confidentiality and integrity impact.","category":"runtime","who_cares":["asp.net-core","kestrel","dotnet","self-hosted","http2"],"confidence":0.8,"analyst_note":"Confirm the affected package list is complete (source table lists 8.0 only for linux-arm and 10.0/9.0 for all RIDs) at https://github.com/advisories/GHSA-fpq8-4vhr-rcxx and https://github.com/dotnet/announcements/issues/462.","how_to_check":"Run dotnet --list-runtimes and dotnet --info to see installed runtime versions; compare the Microsoft.AspNetCore.App.Runtime.* package versions in your projects against the affected ranges.\nCheck project files and packages.lock.json for Microsoft.AspNetCore.App.Runtime.* references at 11.0.0-preview.1 through 11.0.0-rc.1, 10.0.0 through 10.0.12, 9.0.0 through 9.0.20, or 8.0.0 through 8.0.31.\nunknown for whether a given deployment's front-end proxy already normalizes these characters.","needs_analyst":true,"not_affected_if":["managed-hosting","non-http2-only-deployments","default-config"],"severity_if_unknown":"critical"},"cost_usd":0.001247,"input_tokens":8990,"output_tokens":696,"severity_before":"critical"},"analyst_status":null,"analyst_note":null,"search":"'-2026':5A,14A,22A '-444':139B,177B,286C '-70188':6A,15A,23A '/av':275C '/dotnet/announcements/issues/462':263C '/packages/microsoft.aspnetcore.app.runtime.linux-arm)':329C,467C '/packages/microsoft.aspnetcore.app.runtime.linux-arm64)':340C,475C '/packages/microsoft.aspnetcore.app.runtime.linux-musl-arm)':353C,485C '/packages/microsoft.aspnetcore.app.runtime.linux-musl-arm64)':366C,495C '/packages/microsoft.aspnetcore.app.runtime.linux-musl-x64)':379C,505C '/packages/microsoft.aspnetcore.app.runtime.linux-x64)':390C '/packages/microsoft.aspnetcore.app.runtime.osx-arm64)':401C '/packages/microsoft.aspnetcore.app.runtime.osx-x64)':412C '/packages/microsoft.aspnetcore.app.runtime.win-arm)':423C 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An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai"}