🛡️ CVE-2026-45591 — .net

🟠 CVSS 8.0 — High ✅ No Known Exploit CWE-400 NVD
8.0
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

Microsoft Security Advisory CVE-2026-45591 – ASP.NET Core Denial of Service Vulnerability

Executive summary

Microsoft is releasing this security advisory to provide information about a vulnerability in ASP.NET Core SignalR and Blazor Server. This advisory also provides guidance on what developers can do to update their applications to remove this vulnerability.

A denial of service vulnerability exists in the MessagePack hub protocol used by SignalR and Blazor Server where an attacker can send deeply-nested MessagePack arrays to cause a stack overflow, resulting in a denial of service.

Announcement

Announcement for this issue can be found at https://github.com/dotnet/announcements/issues/405

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.linux-arm](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.linux-arm) | >= 10.0.0, <= 10.0.8 | 10.0.9

[Microsoft.AspNetCore.App.Runtime.linux-arm64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.linux-arm64) | >= 10.0.0, <= 10.0.8 | 10.0.9

[Microsoft.AspNetCore.App.Runtime.linux-musl-arm](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.linux-musl-arm) | >= 10.0.0, <= 10.0.8 | 10.0.9

[Microsoft.AspNetCore.App.Runtime.linux-musl-arm64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.linux-musl-arm64) | >= 10.0.0, <= 10.0.8 | 10.0.9

[Microsoft.AspNetCore.App.Runtime.linux-musl-x64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.linux-musl-x64) | >= 10.0.0, <= 10.0.8 | 10.0.9

[Microsoft.AspNetCore.App.Runtime.linux-x64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.linux-x64) | >= 10.0.0, <= 10.0.8 | 10.0.9

[Microsoft.AspNetCore.App.Runtime.osx-arm64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.osx-arm64) | >= 10.0.0, <= 10.0.8 | 10.0.9

[Microsoft.AspNetCore.App.Runtime.osx-x64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.osx-x64) | >= 10.0.0, <= 10.0.8 | 10.0.9

[Microsoft.AspNetCore.App.Runtime.win-arm](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.win-arm) | >= 10.0.0, <= 10.0.8 | 10.0.9

[Microsoft.AspNetCore.App.Runtime.win-arm64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.win-arm64) | >= 10.0.0, <= 10.0.8 | 10.0.9

[Microsoft.AspNetCore.App.Runtime.win-x64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.win-x64) | >= 10.0.0, <= 10.0.8 | 10.0.9

[Microsoft.AspNetCore.App.Runtime.win-x86](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.win-x86) | >= 10.0.0, <= 10.0.8 | 10.0.9

<a name=".NET 10 SignalR"></a>Microsoft.AspNetCore.SignalR.Protocols.MessagePack (.NET 10)

Package name | Affected version | Patched version

------------ | ---------------- | -------------------------

[Microsoft.AspNetCore.SignalR.Protocols.MessagePack](https://www.nuget.org/packages/Microsoft.AspNetCore.SignalR.Protocols.MessagePack) | >= 10.0.0, <= 10.0.8 | 10.0.9

<a name=".NET 9"></a>.NET 9

Package name | Affected version | Patched version

------------ | ---------------- | -------------------------

[Microsoft.AspNetCore.App.Runtime.linux-arm](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.linux-arm) | >= 9.0.0, <= 9.0.16 | 9.0.17

[Microsoft.AspNetCore.App.Runtime.linux-arm64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.linux-arm64) | >= 9.0.0, <= 9.0.16 | 9.0.17

[Microsoft.AspNetCore.App.Runtime.linux-musl-arm](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.linux-musl-arm) | >= 9.0.0, <= 9.0.16 | 9.0.17

[Microsoft.AspNetCore.App.Runtime.linux-musl-arm64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.linux-musl-arm64) | >= 9.0.0, <= 9.0.16 | 9.0.17

[Microsoft.AspNetCore.App.Runtime.linux-musl-x64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.linux-musl-x64) | >= 9.0.0, <= 9.0.16 | 9.0.17

[Microsoft.AspNetCore.App.Runtime.linux-x64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.linux-x64) | >= 9.0.0, <= 9.0.16 | 9.0.17

[Microsoft.AspNetCore.App.Runtime.osx-arm64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.osx-arm64) | >= 9.0.0, <= 9.0.16 | 9.0.17

[Microsoft.AspNetCore.App.Runtime.osx-x64](https://www.nuget.org/packages/Microsoft.AspNetCore.App.Runtime.osx-x64) | >= 9.0.0, <= 9.0.16 | 9.0.17

[Microsoft.AspNetCore.App.Runtime.win-arm](https://www.nuget.org/packages/Microso

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs no privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality none, integrity none, availability high.

Weakness class

CVE-2026-45591 is classified as CWE-400: Uncontrolled Resource Consumption. A request can consume memory, CPU or storage without limit, exhausting capacity for everyone else.

Affected software

CVE-2026-45591 is recorded against 11 packages.

  • .net (from 10.0.0 up to 10.0.9)
  • asp.net-core (from 10.0.0 up to 10.0.9)
  • aspnet-core
  • dotnet
  • dotnet-sdk
  • microsoft.aspnetcore.app.runtime.linux-x64 (from 10.0.0 up to 10.0.9)
  • microsoft.aspnetcore.app.runtime.osx-arm64 (from 10.0.0 up to 10.0.9)
  • microsoft.aspnetcore.app.runtime.win-x64 (from 10.0.0 up to 10.0.9)
  • microsoft.aspnetcore.signalr.protocols.messagepack (from 10.0.0 up to 10.0.9)
  • unknown
  • visual-studio-2026 (from 18.6.0 up to 18.6.3)

Timeline and source

Published on 9 June 2026 and last revised on 23 July 2026. No public exploit is currently recorded for this entry. Record sourced from NVD.

References

msrc.microsoft.com
access.redhat.com
access.redhat.com
access.redhat.com
access.redhat.com
access.redhat.com
access.redhat.com
access.redhat.com
access.redhat.com
access.redhat.com
access.redhat.com
access.redhat.com
access.redhat.com
access.redhat.com
access.redhat.com

CVE-2026-45591 on other distributions

Each distribution ships its own build and its own fixed version. Pick the one you run:

Details

Severity HIGH
CVSS Score 8.0
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CWE CWE-400
Public Exploit ✅ No
Source NVD
Published 2026-06-09
Updated 2026-08-12
Modified 2026-07-23
Fix URL N/A

Affected Packages

Software From version Fixed in
.net 10.0.0 10.0.9
asp.net-core 10.0.0 10.0.9
aspnet-core — —
dotnet — —
dotnet-sdk — —
microsoft.aspnetcore.app.runtime.linux-x64 10.0.0 10.0.9
microsoft.aspnetcore.app.runtime.osx-arm64 10.0.0 10.0.9
microsoft.aspnetcore.app.runtime.win-x64 10.0.0 10.0.9
microsoft.aspnetcore.signalr.protocols.messagepack 10.0.0 10.0.9
unknown — —
visual-studio-2026 18.6.0 18.6.3

References

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