Microsoft Security Advisory CVE-2026-42899 – ASP.NET Core Denial of Service Vulnerability
Date: 2026-05
Affected: nuget/Microsoft.AspNetCore.App.Runtime.osx-x64, nuget/Microsoft.AspNetCore.App.Runtime.osx-x64, nuget/Microsoft.AspNetCore.App.Runtime.osx-arm64
Attack vector: dos
Category: vulnerability-disclosure
Severity: High
CVE: CVE-2026-42899
CWE: CWE-835
CVSS: 7.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H)

## 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 ## <a name="affected-packages"></a>Affected Packages The vulnerability affects any Microsoft .NET project if it uses any of affected package versions listed below ### <a name=".NET 10"></a>.NET 10 Package name | Affected version | Patched version ------------ | ---------------- | ------------------------- [Microsoft.AspNetCore.App.Runtime.win-arm](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.win-arm) | >= 10.0.0, <= 10.0.7 | 10.0.8 [Microsoft.AspNetCore.App.Runtime.win-arm64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.win-arm64) | >= 10.0.0, <= 10.0.7 | 10.0.8 [Microsoft.AspNetCore.App.Runtime.win-x64](https:


Mitigations:

Architectural layers (MAESTRO):