GHSA-9v76-4qcc-frgh Microsoft Security Advisory CVE-2026-42899 – ASP.NET Core Denial of Service Vulnerability

• NuGet Microsoft.AspNetCore.App.Runtime.win-arm: >= 8.0.0, < 8.0.27 → fixed in 8.0.27 • NuGet Microsoft.AspNetCore.App.Runtime.win-arm64: >= 8.0.0, < 8.0.27 → fixed in 8.0.27 • NuGet Microsoft.AspNetCore.App.Runtime.win-x64: >= 8.0.0, < 8.0.27 → fixed in 8.0.27 • NuGet Microsoft.AspNetCore.App.Runtime.win-x86: >= 8.0.0, < 8.0.27 → fixed in 8.0.27 • NuGet Microsoft.AspNetCore.App.Runtime.linux-arm: >= 8.0.0, < 8.0.27 → fixed in 8.0.27 • NuGet Microsoft.AspNetCore.App.Runtime.linux-arm64: >= 8.0.0, < 8.0.27 → fixed in 8.0.27 • NuGet Microsoft.AspNetCore.App.Runtime.linux-musl-arm: >= 8.0.0, < 8.0.27 → fixed in 8.0.27 • NuGet Microsoft.AspNetCore.App.Runtime.linux-musl-arm64: >= 8.0.0, < 8.0.27 → fixed in 8.0.27 • NuGet Microsoft.AspNetCore.App.Runtime.linux-musl-x64: >= 8.0.0, < 8.0.27 → fixed in 8.0.27 • NuGet Microsoft.AspNetCore.App.Runtime.linux-x64: >= 8.0.0, < 8.0.27 → fixed in 8.0.27 • NuGet Microsoft.AspNetCore.App.Runtime.osx-arm64: >= 8.0.0, < 8.0.27 → fixed in 8.0.27 • NuGet Microsoft.AspNetCore.App.Runtime.osx-x64: >= 8.0.0, < 8.0.27 → fixed in 8.0.27 • NuGet Microsoft.AspNetCore.App.Runtime.win-arm: >= 9.0.0, < 9.0.16 → fixed in 9.0.16 • NuGet Microsoft.AspNetCore.App.Runtime.win-arm: >= 10.0.0, < 10.0.8 → fixed in 10.0.8 • NuGet Microsoft.AspNetCore.App.Runtime.win-arm64: >= 9.0.0, < 9.0.16 → fixed in 9.0.16 • NuGet Microsoft.AspNetCore.App.Runtime.win-arm64: >= 10.0.0, < 10.0.8 → fixed in 10.0.8 • NuGet Microsoft.AspNetCore.App.Runtime.win-x64: >= 9.0.0, < 9.0.16 → fixed in 9.0.16 • NuGet Microsoft.AspNetCore.App.Runtime.win-x64: >= 10.0.0, < 10.0.8 → fixed in 10.0.8 • NuGet Microsoft.AspNetCore.App.Runtime.win-x86: >= 9.0.0, < 9.0.16 → fixed in 9.0.16 • NuGet Microsoft.AspNetCore.App.Runtime.win-x86: >= 10.0.0, < 10.0.8 → fixed in 10.0.8 • NuGet Microsoft.AspNetCore.App.Runtime.linux-arm: >= 9.0.0, < 9.0.16 → fixed in 9.0.16 • NuGet Microsoft.AspNetCore.App.Runtime.linux-arm: >= 10.0.0, < 10.0.8 → fixed in 10.0.8 • NuGet Microsoft.AspNetCore.App.Runtime.linux-arm64: >= 9.0.0, < 9.0.16 → fixed in 9.0.16 • NuGet Microsoft.AspNetCore.App.Runtime.linux-arm64: >= 10.0.0, < 10.0.8 → fixed in 10.0.8 • NuGet Microsoft.AspNetCore.App.Runtime.linux-musl-arm: >= 9.0.0, < 9.0.16 → fixed in 9.0.16 • NuGet Microsoft.AspNetCore.App.Runtime.linux-musl-arm: >= 10.0.0, < 10.0.8 → fixed in 10.0.8 • NuGet Microsoft.AspNetCore.App.Runtime.linux-musl-arm64: >= 9.0.0, < 9.0.16 → fixed in 9.0.16 • NuGet Microsoft.AspNetCore.App.Runtime.linux-musl-arm64: >= 10.0.0, < 10.0.8 → fixed in 10.0.8 • NuGet Microsoft.AspNetCore.App.Runtime.linux-musl-x64: >= 10.0.0, < 10.0.8 → fixed in 10.0.8 • NuGet Microsoft.AspNetCore.App.Runtime.linux-musl-x64: >= 9.0.0, < 9.0.16 → fixed in 9.0.16 • NuGet Microsoft.AspNetCore.App.Runtime.linux-x64: >= 9.0.0, < 9.0.16 → fixed in 9.0.16 • NuGet Microsoft.AspNetCore.App.Runtime.linux-x64: >= 10.0.0, < 10.0.8 → fixed in 10.0.8 • NuGet Microsoft.AspNetCore.App.Runtime.osx-arm64: >= 9.0.0, < 9.0.16 → fixed in 9.0.16 • NuGet Microsoft.AspNetCore.App.Runtime.osx-arm64: >= 10.0.0, < 10.0.8 → fixed in 10.0.8 • NuGet Microsoft.AspNetCore.App.Runtime.osx-x64: >= 9.0.0, < 9.0.16 → fixed in 9.0.16 • NuGet Microsoft.AspNetCore.App.Runtime.osx-x64: >= 10.0.0, < 10.0.8 → fixed in 10.0.8

Executive Summary: Microsoft is releasing this security advisory to provide information about a vulnerability in .NET 8.0, .NET 9.0, and .NET 10.0. This advisory also provides guidance on what developers can do to update their applications to remove this vulnerability. Loop with unreachable exit condition ('infinite loop') in ASP.NET Core allows an unauthorized attacker to deny service over a network. Announcement Announcement for this issue can be found at https://github.com/dotnet/announcements/issues/397 CVSS Details • Version: 3.1 • Severity: • Score: 7.5 • Vector: AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:U/RL:O/RC:C • Weakness: CWE-835: Loop with Unreachable Exit Condition ('Infinite Loop') Affected Platforms • Platforms: All • Architectures: All Affected Packages The vulnerability affects any Microsoft .NET project if it uses any of affected package versions listed below .NET 10 Package name | Affected version | Patched version ------------ | ---------------- | ------------------------- Microsoft.AspNetCore.App.Runtime.win-arm | >= 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, .NET 9 Package name | Affected version | Patched version ------------ | ---------------- | ------------------------- Microsoft.AspNetCore.App.Runtime.win-arm | >= 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, .NET 8 Package name | Affected version | Patched version ------------ | ---------------- | ------------------------- Microsoft.AspNetCore.App.Runtime.win-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, How do I know if I am affected? If using a package listed in affected packages, an application is exposed to the vulnerability. How do I fix the issue? 1. To fix the issue please install the latest version of .NET 8.0, NET 9.0, or .NET 10.0, as appropriate. If developers have installed one or more .NET SDKs through Visual Studio, Visual Studio will prompt them to update Visual Studio, which will also update the application's .NET SDKs. 2. If an application references the vulnerable package, update the package reference to the patched version. Developers can list the versio…