Microsoft Security Advisory CVE-2026-69304 – ASP.NET Core Denial of Service Vulnerability

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

5.9 · CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS

• CVE-2026-69304: 0.85% estimated exploitation activity in the next 30 days; percentile 58.40 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Microsoft Security Advisory CVE-2026-69304 – 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 IIS out-of-process hosting and request decompression. This advisory also provides guidance on what developers can do to update their applications to remove this vulnerability. The IIS Middleware for ASP.NET Core did not properly constrain decompression of certain types of request, leading to excess memory consumption and a Denial of Service. Announcement Announcement for this issue can be found at https://github.com/dotnet/announcements/issues/443 CVSS Details - Version: 3.1 - Severity: Medium - Score: 5.9 - Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H - Weakness: CWE-409 (Improper Handling of Highly Compressed Data (Data Amplification)) Affected Platforms - Platforms: Windows / IIS out-of-process - Architectures: All <a name="affected-packages"</aAffected Packages…

Published by the source

9 Sep 2026, 16:04 UTC

Last modified by the source

1 Oct 2026, 12:55 UTC

Source last checked

26 Oct 2026, 17:05 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-8cp2-47hg-mfgh

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-8cp2-47hg-mfgh

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# Patch Next advisory brief: CVE-2026-69304

Advisory: Microsoft Security Advisory CVE-2026-69304 – ASP.NET Core Denial of Service Vulnerability
IDs: CVE-2026-69304, GHSA-8cp2-47hg-mfgh
Record: https://patchnext.com/advisories/cve-2026-69304 (revision 2, source checked 26 Oct 2026, 17:05 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.9)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: microsoft.aspnetcore.server.iisintegration 11.0.0-rc.1, 10.0.12, 9.0.20, 8.0.31. A vendor fix does not mean a deployment is fixed.

## Affected components
- NuGet microsoft.aspnetcore.server.iisintegration: affected >= 11.0.0-preview.1, < 11.0.0-rc.1; >= 8.0.0, <= 8.0.30; >= 9.0.0, <= 9.0.19; >= 10.0.0, <= 10.0.11; fixed in 9.0.20, 10.0.12, 11.0.0-rc.1, 8.0.31

## Suggested inspection (read-only)
- NuGet microsoft.aspnetcore.server.iisintegration: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on microsoft.aspnetcore.server.iisintegration.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-8cp2-47hg-mfgh (OSV record GHSA-8cp2-47hg-mfgh lists affected ranges: NuGet microsoft.aspnetcore.server.iisintegration >=11.0.0-preview.1 =8.0.0 =9.0.0 =10.0.0 <10.0.12 (fixed))
- Verified: https://github.com/advisories/GHSA-8cp2-47hg-mfgh (GitHub-reviewed advisory GHSA-8cp2-47hg-mfgh lists affected ranges: NuGet microsoft.aspnetcore.server.iisintegration >=11.0.0-preview.1 =8.0.0 =9.0.0 =10.0.0 <=10.0.11)

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