Microsoft Security Advisory CVE-2026-118749 - ASP.NET Core Denial of Service Vulnerability

Exploitation

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

CVSS

7.5 · 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

EPSS

No dated EPSS signal available.

As published by the source; long descriptions are shortened.

Executive summary Microsoft is releasing this security advisory to provide information about a vulnerability in ASP.NET Core. This advisory provides guidance on updating affected applications and components. Minimal API validation repeatedly copies a growing validation-error dictionary, allowing attacker-controlled collections to trigger quadratic CPU work after the client disconnects.

Announcement Announcement for this issue can be found at https://github.com/dotnet/announcements/issues/505

CVSS Details - Version: 3.1 - Severity: High - Score: 7.5 (base score) - 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` - Weakness: CWE-407

Affected Platforms - Platforms: Windows, Linux, macOS - Architectures: All

Affected Packages The tables list affected version ranges and fixed package versions. Runtime and standalone deliveries are listed separately.

.NET 11.0 - affected runtime packages Package | Affected version | Patched…

Published by the source

10 Nov 2026, 23:08 UTC

Last modified by the source

10 Nov 2026, 23:30 UTC

Source last checked

11 Nov 2026, 07:45 UTC

1. Revision 2 · amended · 11 Nov 2026

   Amended from osv record GHSA-m28h-pj36-4364

2. Revision 1 · created · 11 Nov 2026

   Published from ghsa record GHSA-m28h-pj36-4364

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# Patch Next advisory brief: CVE-2026-118749

Advisory: Microsoft Security Advisory CVE-2026-118749 - ASP.NET Core Denial of Service Vulnerability
IDs: CVE-2026-118749, GHSA-m28h-pj36-4364
Record: https://patchnext.com/advisories/cve-2026-118749 (revision 2, source checked 11 Nov 2026, 07:45 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: microsoft.aspnetcore.app.runtime.linux-arm64 11.0.0; microsoft.aspnetcore.app.runtime.linux-musl-arm64 11.0.0; microsoft.aspnetcore.app.runtime.osx-x64 11.0.0; microsoft.aspnetcore.app.runtime.linux-arm 11.0.0; microsoft.aspnetcore.app.runtime.win-x86 11.0.0; microsoft.aspnetcore.app.runtime.linux-x64 11.0.0; microsoft.aspnetcore.app.runtime.linux-musl-arm 11.0.0; microsoft.aspnetcore.app.runtime.linux-musl-x64 11.0.0; microsoft.aspnetcore.app.runtime.osx-arm64 11.0.0; microsoft.aspnetcore.app.runtime.win-x64 11.0.0; microsoft.extensions.validation 11.0.0; microsoft.aspnetcore.app.runtime.win-arm64 11.0.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- NuGet microsoft.aspnetcore.app.runtime.linux-arm64: affected >= 11.0.0-rc.1.26425.128, < 11.0.0; fixed in 11.0.0
- NuGet microsoft.aspnetcore.app.runtime.linux-musl-arm64: affected >= 11.0.0-rc.1.26425.128, < 11.0.0; fixed in 11.0.0
- NuGet microsoft.aspnetcore.app.runtime.osx-x64: affected >= 11.0.0-rc.1.26425.128, < 11.0.0; fixed in 11.0.0
- NuGet microsoft.aspnetcore.app.runtime.linux-arm: affected >= 11.0.0-rc.1.26425.128, < 11.0.0; fixed in 11.0.0
- NuGet microsoft.aspnetcore.app.runtime.win-x86: affected >= 11.0.0-rc.1.26425.128, < 11.0.0; fixed in 11.0.0
- NuGet microsoft.aspnetcore.app.runtime.linux-x64: affected >= 11.0.0-rc.1.26425.128, < 11.0.0; fixed in 11.0.0
- NuGet microsoft.aspnetcore.app.runtime.linux-musl-arm: affected >= 11.0.0-rc.1.26425.128, < 11.0.0; fixed in 11.0.0
- NuGet microsoft.aspnetcore.app.runtime.linux-musl-x64: affected >= 11.0.0-rc.1.26425.128, < 11.0.0; fixed in 11.0.0
- NuGet microsoft.aspnetcore.app.runtime.osx-arm64: affected >= 11.0.0-rc.1.26425.128, < 11.0.0; fixed in 11.0.0
- NuGet microsoft.aspnetcore.app.runtime.win-x64: affected >= 11.0.0-rc.1.26425.128, < 11.0.0; fixed in 11.0.0
- NuGet microsoft.extensions.validation: affected >= 11.0.0-rc.1.26425.128, < 11.0.0; fixed in 11.0.0
- NuGet microsoft.aspnetcore.app.runtime.win-arm64: affected >= 11.0.0-rc.1.26425.128, < 11.0.0; fixed in 11.0.0

## Suggested inspection (read-only)
- NuGet microsoft.aspnetcore.app.runtime.linux-arm64: check the installed version with your package manager.
- NuGet microsoft.aspnetcore.app.runtime.linux-musl-arm64: check the installed version with your package manager.
- NuGet microsoft.aspnetcore.app.runtime.osx-x64: check the installed version with your package manager.
- NuGet microsoft.aspnetcore.app.runtime.linux-arm: check the installed version with your package manager.
- NuGet microsoft.aspnetcore.app.runtime.win-x86: check the installed version with your package manager.
- NuGet microsoft.aspnetcore.app.runtime.linux-x64: check the installed version with your package manager.
- NuGet microsoft.aspnetcore.app.runtime.linux-musl-arm: check the installed version with your package manager.
- NuGet microsoft.aspnetcore.app.runtime.linux-musl-x64: check the installed version with your package manager.
- NuGet microsoft.aspnetcore.app.runtime.osx-arm64: check the installed version with your package manager.
- NuGet microsoft.aspnetcore.app.runtime.win-x64: check the installed version with your package manager.
- NuGet microsoft.extensions.validation: check the installed version with your package manager.
- NuGet microsoft.aspnetcore.app.runtime.win-arm64: 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.app.runtime.linux-arm64, microsoft.aspnetcore.app.runtime.linux-musl-arm64, microsoft.aspnetcore.app.runtime.osx-x64, microsoft.aspnetcore.app.runtime.linux-arm, microsoft.aspnetcore.app.runtime.win-x86, microsoft.aspnetcore.app.runtime.linux-x64, microsoft.aspnetcore.app.runtime.linux-musl-arm, microsoft.aspnetcore.app.runtime.linux-musl-x64, microsoft.aspnetcore.app.runtime.osx-arm64, microsoft.aspnetcore.app.runtime.win-x64, microsoft.extensions.validation, microsoft.aspnetcore.app.runtime.win-arm64.
- 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://github.com/advisories/GHSA-m28h-pj36-4364 (GitHub-reviewed advisory GHSA-m28h-pj36-4364 lists affected ranges: NuGet microsoft.aspnetcore.app.runtime.linux-arm >=11.0.0-rc.1.26425.128 =11.0.0-rc.1.26425.128 =11.0.0-rc.1.26425.128 =11.0.0-rc.1.26425.128 <=11.0.0-rc.3.26522.148; NuGet…)
- Verified: https://osv.dev/vulnerability/GHSA-m28h-pj36-4364 (OSV record GHSA-m28h-pj36-4364 lists affected ranges: NuGet microsoft.aspnetcore.app.runtime.linux-arm >=11.0.0-rc.1.26425.128 =11.0.0-rc.1.26425.128 =11.0.0-rc.1.26425.128 =11.0.0-rc.1.26425.128 <11.0.0 (fixed); NuGet microsoft.aspnetcore.app.runtime.linux-musl-x64…)

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