CVE-2026-69304

ASP.NET Core Denial of Service Vulnerability

CVE-2026-69304 is fixed in 12 products on 2 platforms, first by Microsoft ASP.NET Core Hosting Bundle 9.0 9.0.20, released August 14, 2026. 3 other affected products have no fix yet. It is not reported as exploited. Patch Radar priority: Routine.

RoutineFixed on 2 platforms

CVSS

5.9

Important

Exploitation

None reported

Exploitation Less Likely

CISA KEV

Not listed

Not in the Known Exploited Vulnerabilities catalog

EPSS

0.0086

58th percentile

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

Where it's fixed

Product	Fixed in	Fix	Released
Microsoft
.NET 10.0 runtime installed on Windows		KB5126106	Sep 8, 2026
.NET 8.0 runtime installed on Windows		KB5126104	Sep 8, 2026
.NET 9.0 runtime installed on Windows		KB5126105	Sep 8, 2026
ASP.NET Core 10.0		KB5126106	Sep 8, 2026
ASP.NET Core 8.0		KB5126104	Sep 8, 2026
ASP.NET Core 9.0		KB5126105	Sep 8, 2026
Windows apps
Microsoft .NET Windows Desktop Runtime 10.0	10.0.12	Microsoft .NET Windows Desktop Runtime 10.0 10.0.12	Aug 22, 2026
Microsoft .NET Windows Desktop Runtime 8.0	8.0.31	Microsoft .NET Windows Desktop Runtime 8.0 8.0.31	Aug 22, 2026
Microsoft .NET Windows Desktop Runtime 9.0	9.0.20	Microsoft .NET Windows Desktop Runtime 9.0 9.0.20	Aug 21, 2026
Microsoft ASP.NET Core Hosting Bundle 10.0	10.0.12	Microsoft ASP.NET Core Hosting Bundle 10.0 10.0.12	Aug 22, 2026
Microsoft ASP.NET Core Hosting Bundle 8.0	8.0.31	Microsoft ASP.NET Core Hosting Bundle 8.0 8.0.31	Aug 22, 2026
Microsoft ASP.NET Core Hosting Bundle 9.0	9.0.20	Microsoft ASP.NET Core Hosting Bundle 9.0 9.0.20	Aug 14, 2026
No fix yet
Microsoft Windows Desktop Runtime - 8.0.25 (arm64) (Windows apps)	No fix yet	no-fix	n/a
Microsoft Windows Desktop Runtime - 8.0.25 (x64) (Windows apps)	No fix yet	no-fix	n/a
Microsoft Windows Desktop Runtime - 8.0.25 (x86) (Windows apps)	No fix yet	no-fix	n/a

Details

Published
September 8, 2026
Weakness
Improper Handling of Highly Compressed Data (Data Amplification)
Vendor advisory
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-69304

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