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Advisory record · GHSA-9v76-4qcc-frgh

Microsoft Security Advisory CVE-2026-42899 – ASP.NET Core Denial of Service Vulnerability

CVSS 7.5 HighEPSS 0.024 · 84th percentile

Published by the GitHub Advisory Database at 18 May 2026, 19:10 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

PackageEcosystemAffectedFixed in
Microsoft.AspNetCore.App.Runtime.win-armNuGet>=8.0.0, <8.0.27 || >=9.0.0, <9.0.16 || >=10.0.0, <10.0.88.0.27, 9.0.16, 10.0.8
Microsoft.AspNetCore.App.Runtime.win-arm64NuGet>=8.0.0, <8.0.27 || >=9.0.0, <9.0.16 || >=10.0.0, <10.0.88.0.27, 9.0.16, 10.0.8
Microsoft.AspNetCore.App.Runtime.win-x64NuGet>=8.0.0, <8.0.27 || >=9.0.0, <9.0.16 || >=10.0.0, <10.0.88.0.27, 9.0.16, 10.0.8
Microsoft.AspNetCore.App.Runtime.win-x86NuGet>=8.0.0, <8.0.27 || >=9.0.0, <9.0.16 || >=10.0.0, <10.0.88.0.27, 9.0.16, 10.0.8
Microsoft.AspNetCore.App.Runtime.linux-armNuGet>=8.0.0, <8.0.27 || >=9.0.0, <9.0.16 || >=10.0.0, <10.0.88.0.27, 9.0.16, 10.0.8
Microsoft.AspNetCore.App.Runtime.linux-arm64NuGet>=8.0.0, <8.0.27 || >=9.0.0, <9.0.16 || >=10.0.0, <10.0.88.0.27, 9.0.16, 10.0.8
Microsoft.AspNetCore.App.Runtime.linux-musl-armNuGet>=8.0.0, <8.0.27 || >=9.0.0, <9.0.16 || >=10.0.0, <10.0.88.0.27, 9.0.16, 10.0.8
Microsoft.AspNetCore.App.Runtime.linux-musl-arm64NuGet>=8.0.0, <8.0.27 || >=9.0.0, <9.0.16 || >=10.0.0, <10.0.88.0.27, 9.0.16, 10.0.8
Microsoft.AspNetCore.App.Runtime.linux-musl-x64NuGet>=8.0.0, <8.0.27 || >=10.0.0, <10.0.8 || >=9.0.0, <9.0.168.0.27, 10.0.8, 9.0.16
Microsoft.AspNetCore.App.Runtime.linux-x64NuGet>=8.0.0, <8.0.27 || >=9.0.0, <9.0.16 || >=10.0.0, <10.0.88.0.27, 9.0.16, 10.0.8
Microsoft.AspNetCore.App.Runtime.osx-arm64NuGet>=8.0.0, <8.0.27 || >=9.0.0, <9.0.16 || >=10.0.0, <10.0.88.0.27, 9.0.16, 10.0.8
Microsoft.AspNetCore.App.Runtime.osx-x64NuGet>=8.0.0, <8.0.27 || >=9.0.0, <9.0.16 || >=10.0.0, <10.0.88.0.27, 9.0.16, 10.0.8
Identifiers
GHSA-9v76-4qcc-frgh · BIT-dotnet-2026-42899 · BIT-dotnet-sdk-2026-42899 · CVE-2026-42899
Weakness (CWE)
CWE-835
Tags
Published
18 May 2026
Updated
10 Sept 2026

Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

The ASP.NET Core runtime packages Microsoft.AspNetCore.App.Runtime (across Windows, Linux and musl targets) are affected in versions 8.0.0 to before 8.0.27, 9.0.0 to before 9.0.16, and 10.0.0 to before 10.0.8. An unauthenticated attacker over a network can trigger an infinite loop in ASP.NET Core and deny service. Upgrade to 8.0.27, 9.0.16, or 10.0.8, depending on your .NET version.

Written 9 Nov 2026.

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

ScoreRatingCVSSVectorSource
7.5 High 3.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:U/RL:O/RC:C CNA (microsoft)
  • CISA KEV Not listed.
  • EPSS 0.024, the 84th percentile, on 9 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

  1. 12 May 2026, 18:02 UTC Published by the maintainers as a GitHub repository advisory
  2. 31 Oct 2026, 15:21 UTC First seen by agentprime
  3. 31 Oct 2026, 15:21 UTC Confirmed by OSV

Sources

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.