GHSA-fpq8-4vhr-rcxx Microsoft Security Advisory CVE-2026-70188 - ASP.NET Core Security Feature Bypass Vulnerability

• NuGet Microsoft.AspNetCore.App.Runtime.linux-arm: >= 11.0.0-preview.1, < 11.0.0-rc.2 → fixed in 11.0.0-rc.2 • NuGet Microsoft.AspNetCore.App.Runtime.linux-arm64: >= 11.0.0-preview.1, < 11.0.0-rc.2 → fixed in 11.0.0-rc.2 • NuGet Microsoft.AspNetCore.App.Runtime.linux-musl-arm: >= 11.0.0-preview.1, < 11.0.0-rc.2 → fixed in 11.0.0-rc.2 • NuGet Microsoft.AspNetCore.App.Runtime.linux-musl-arm64: >= 11.0.0-preview.1, < 11.0.0-rc.2 → fixed in 11.0.0-rc.2 • NuGet Microsoft.AspNetCore.App.Runtime.linux-musl-x64: >= 11.0.0-preview.1, < 11.0.0-rc.2 → fixed in 11.0.0-rc.2 • NuGet Microsoft.AspNetCore.App.Runtime.linux-x64: >= 11.0.0-preview.1, < 11.0.0-rc.2 → fixed in 11.0.0-rc.2 • NuGet Microsoft.AspNetCore.App.Runtime.osx-arm64: >= 11.0.0-preview.1, < 11.0.0-rc.2 → fixed in 11.0.0-rc.2 • NuGet Microsoft.AspNetCore.App.Runtime.osx-x64: >= 11.0.0-preview.1, < 11.0.0-rc.2 → fixed in 11.0.0-rc.2 • NuGet Microsoft.AspNetCore.App.Runtime.win-arm64: >= 11.0.0-preview.1, < 11.0.0-rc.2 → fixed in 11.0.0-rc.2 • NuGet Microsoft.AspNetCore.App.Runtime.win-x64: >= 11.0.0-preview.1, < 11.0.0-rc.2 → fixed in 11.0.0-rc.2 • NuGet Microsoft.AspNetCore.App.Runtime.win-x86: >= 11.0.0-preview.1, < 11.0.0-rc.2 → fixed in 11.0.0-rc.2 • NuGet Microsoft.AspNetCore.App.Runtime.linux-arm: >= 8.0.0, < 8.0.32 → fixed in 8.0.32 • NuGet Microsoft.AspNetCore.App.Runtime.linux-arm64: >= 8.0.0, < 8.0.32 → fixed in 8.0.32 • NuGet Microsoft.AspNetCore.App.Runtime.linux-musl-arm: >= 8.0.0, < 8.0.32 → fixed in 8.0.32 • NuGet Microsoft.AspNetCore.App.Runtime.linux-musl-arm64: >= 8.0.0, < 8.0.32 → fixed in 8.0.32 • NuGet Microsoft.AspNetCore.App.Runtime.linux-musl-x64: >= 8.0.0, < 8.0.32 → fixed in 8.0.32 • NuGet Microsoft.AspNetCore.App.Runtime.linux-x64: >= 8.0.0, < 8.0.32 → fixed in 8.0.32 • NuGet Microsoft.AspNetCore.App.Runtime.osx-arm64: >= 8.0.0, < 8.0.32 → fixed in 8.0.32 • NuGet Microsoft.AspNetCore.App.Runtime.osx-x64: >= 8.0.0, < 8.0.32 → fixed in 8.0.32 • NuGet Microsoft.AspNetCore.App.Runtime.win-arm64: >= 8.0.0, < 8.0.32 → fixed in 8.0.32 • NuGet Microsoft.AspNetCore.App.Runtime.win-x64: >= 8.0.0, < 8.0.32 → fixed in 8.0.32 • NuGet Microsoft.AspNetCore.App.Runtime.win-x86: >= 8.0.0, < 8.0.32 → fixed in 8.0.32 • NuGet Microsoft.AspNetCore.App.Runtime.linux-arm: >= 10.0.0, < 10.0.13 → fixed in 10.0.13 • NuGet Microsoft.AspNetCore.App.Runtime.linux-arm64: >= 10.0.0, < 10.0.13 → fixed in 10.0.13 • NuGet Microsoft.AspNetCore.App.Runtime.linux-musl-arm: >= 10.0.0, < 10.0.13 → fixed in 10.0.13 • NuGet Microsoft.AspNetCore.App.Runtime.linux-musl-arm64: >= 10.0.0, < 10.0.13 → fixed in 10.0.13 • NuGet Microsoft.AspNetCore.App.Runtime.linux-musl-x64: >= 10.0.0, < 10.0.13 → fixed in 10.0.13 • NuGet Microsoft.AspNetCore.App.Runtime.linux-x64: >= 10.0.0, < 10.0.13 → fixed in 10.0.13 • NuGet Microsoft.AspNetCore.App.Runtime.osx-arm64: >= 10.0.0, < 10.0.13 → fixed in 10.0.13 • NuGet Microsoft.AspNetCore.App.Runtime.osx-x64: >= 10.0.0, < 10.0.13 → fixed in 10.0.13 • NuGet Microsoft.AspNetCore.App.Runtime.win-arm64: >= 10.0.0, < 10.0.13 → fixed in 10.0.13 • NuGet Microsoft.AspNetCore.App.Runtime.win-x64: >= 10.0.0, < 10.0.13 → fixed in 10.0.13 • NuGet Microsoft.AspNetCore.App.Runtime.win-x86: >= 10.0.0, < 10.0.13 → fixed in 10.0.13 • NuGet Microsoft.AspNetCore.App.Runtime.linux-arm: >= 9.0.0, < 9.0.21 → fixed in 9.0.21 • NuGet Microsoft.AspNetCore.App.Runtime.linux-arm64: >= 9.0.0, < 9.0.21 → fixed in 9.0.21 • NuGet Microsoft.AspNetCore.App.Runtime.linux-musl-arm: >= 9.0.0, < 9.0.21 → fixed in 9.0.21 • NuGet Microsoft.AspNetCore.App.Runtime.linux-musl-arm64: >= 9.0.0, < 9.0.21 → fixed in 9.0.21 • NuGet Microsoft.AspNetCore.App.Runtime.linux-musl-x64: >= 9.0.0, < 9.0.21 → fixed in 9.0.21 • NuGet Microsoft.AspNetCore.App.Runtime.linux-x64: >= 9.0.0, < 9.0.21 → fixed in 9.0.21 • NuGet Microsoft.AspNetCore.App.Runtime.osx-arm64: >= 9.0.0, < 9.0.21 → fixed in 9.0.21 • NuGet Microsoft.AspNetCore.App.Runtime.osx-x64: >= 9.0.0, < 9.0.21 → fixed in 9.0.21 • NuGet Microsoft.AspNetCore.App.Runtime.win-arm64: >= 9.0.0, < 9.0.21 → fixed in 9.0.21 • NuGet Microsoft.AspNetCore.App.Runtime.win-x64: >= 9.0.0, < 9.0.21 → fixed in 9.0.21 • NuGet Microsoft.AspNetCore.App.Runtime.win-x86: >= 9.0.0, < 9.0.21 → fixed in 9.0.21

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. Kestrel accepts newline characters in HTTP/2 request trailers and values retrieved from the dynamic HPACK table instead of treating them as malformed. Announcement Announcement for this issue can be found at https://github.com/dotnet/announcements/issues/462 CVSS Details • Version: 3.1 • Severity: Critical • Score: 9.1 • Vector: `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N` • Weakness: CWE-444 (Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')) Affected Platforms • Platforms: Windows, Linux, macOS • 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 | >= 11.0.0-preview.1, = 11.0.0-preview.1, = 11.0.0-preview.1, = 11.0.0-preview.1, = 11.0.0-preview.1, = 11.0.0-preview.1, = 11.0.0-preview.1, = 11.0.0-preview.1, = 11.0.0-preview.1, = 11.0.0-preview.1, = 11.0.0-preview.1, = 11.0.0-preview.1, = 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, <= 9.0.20 | …