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Microsoft Security Response CenterCVE-2026-69304

ASP.NET Core Denial of Service Vulnerability

Improper handling of highly compressed data (data amplification) in ASP.NET Core allows an unauthorized attacker to deny service over a network.

Read the vendor bulletin Get alerts for ASP.NET Core
5.9CVSS out of 10High severity
Scope

What the vendor says is affected

  • ASP.NET Core 11.0
  • .NET 10.0 installed on Windows
  • .NET 9.0 installed on Windows
  • .NET 8.0 installed on Windows
  • Microsoft Visual Studio 2026 version 18.9
  • Microsoft Visual Studio 2022 version 17.14
  • ASP.NET Core 9.0
  • ASP.NET Core 10.0
  • ASP.NET Core 8.0

Versions the vendor lists as fixed

  • 11.0 RC1
  • 10.0.12
  • 9.0.20
  • 8.0.31
  • 18.9.3
  • 17.14.40
Next step

What the vendor recommends

Release Notes Install KB5126106. Install KB5126105. Install KB5126104.

Review the complete instructions on the vendor's site
Timeline

When this advisory changed

  1. Published by Microsoft Security Response Center

    The publication date reported by the vendor.

  2. Added to SecurityAlert

    We collected the advisory from the official source.

  3. Confirmed at the source

    Our collector saw this advisory during a later source check.

Vulnerabilities

CVEs named in this advisory

CVE-2026-69304View CVSS, KEV, EPSS, and threat context
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