Microsoft Security Advisory CVE-2026-70197 - .NET and Visual Studio Remote Code Execution Vulnerability

Exploitation

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

CVSS

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

EPSS

• CVE-2026-70197: 0.79% estimated exploitation activity in the next 30 days; percentile 56.26 (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.

Executive summary Microsoft is releasing this security advisory to provide information about a vulnerability in System.Net.Sockets. This advisory also provides guidance on what developers can do to update their applications to remove this vulnerability. On Windows, reusing a `SocketAsyncEventArgs` instance across IPv4 and IPv6 datagram sockets can retain an undersized cached native address buffer, allowing an unauthenticated out-of-bounds write during `ReceiveFromAsync`.

Announcement Announcement for this issue can be found at https://github.com/dotnet/announcements/issues/466

CVSS Details - Version: 3.1 - Severity: High - Score: 8.1 - Vector: `CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H` - Weakness: CWE-787 (Out-of-bounds Write)

Affected Platforms - Platforms: Windows - Architectures: All

Affected Packages The vulnerability affects Microsoft .NET projects that use an affected package version listed below. Package name | Affected version |…

Published by the source

13 Oct 2026, 20:34 UTC

Last modified by the source

3 Nov 2026, 17:15 UTC

Source last checked

4 Nov 2026, 06:40 UTC

1. Revision 4 · amended · 4 Nov 2026

   Amended from osv record GHSA-4mpw-cpwj-hxxj

2. Revision 3 · amended · 3 Nov 2026

   Amended from ghsa record GHSA-4mpw-cpwj-hxxj

3. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-4mpw-cpwj-hxxj

4. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-4mpw-cpwj-hxxj

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# Patch Next advisory brief: CVE-2026-70197

Advisory: Microsoft Security Advisory CVE-2026-70197 - .NET and Visual Studio Remote Code Execution Vulnerability
IDs: CVE-2026-70197, GHSA-4mpw-cpwj-hxxj
Record: https://patchnext.com/advisories/cve-2026-70197 (revision 4, source checked 4 Nov 2026, 06:40 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: microsoft.netcore.app.runtime.win-x86 11.0.0-rc.3.26522.148, 10.0.14, 9.0.22, 8.0.33; microsoft.netcore.app.runtime.win-arm64 11.0.0-rc.3.26522.148, 10.0.14, 9.0.22, 8.0.33; microsoft.netcore.app.runtime.win-x64 11.0.0-rc.3.26522.148, 10.0.14, 9.0.22, 8.0.33. A vendor fix does not mean a deployment is fixed.

## Affected components
- NuGet microsoft.netcore.app.runtime.win-x86: affected >= 8.0.0, < 8.0.33; >= 11.0.0-preview.1, < 11.0.0-rc.3.26522.148; >= 9.0.0, < 9.0.22; >= 10.0.0, < 10.0.14; fixed in 8.0.33, 9.0.22, 11.0.0-rc.3.26522.148, 10.0.14
- NuGet microsoft.netcore.app.runtime.win-arm64: affected >= 8.0.0, < 8.0.33; >= 11.0.0-preview.1, < 11.0.0-rc.3.26522.148; >= 9.0.0, < 9.0.22; >= 10.0.0, < 10.0.14; fixed in 8.0.33, 9.0.22, 11.0.0-rc.3.26522.148, 10.0.14
- NuGet microsoft.netcore.app.runtime.win-x64: affected >= 8.0.0, < 8.0.33; >= 11.0.0-preview.1, < 11.0.0-rc.3.26522.148; >= 9.0.0, < 9.0.22; >= 10.0.0, < 10.0.14; fixed in 8.0.33, 9.0.22, 11.0.0-rc.3.26522.148, 10.0.14

## Suggested inspection (read-only)
- NuGet microsoft.netcore.app.runtime.win-x86: check the installed version with your package manager.
- NuGet microsoft.netcore.app.runtime.win-arm64: check the installed version with your package manager.
- NuGet microsoft.netcore.app.runtime.win-x64: 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.netcore.app.runtime.win-x86, microsoft.netcore.app.runtime.win-arm64, microsoft.netcore.app.runtime.win-x64.
- 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-4mpw-cpwj-hxxj (OSV record GHSA-4mpw-cpwj-hxxj lists affected ranges: NuGet microsoft.netcore.app.runtime.win-arm64 >=8.0.0 =11.0.0-preview.1 =9.0.0 =10.0.0 =8.0.0 =11.0.0-preview.1 =9.0.0 =10.0.0 =8.0.0 =11.0.0-preview.1 =9.0.0…)
- Verified: https://github.com/advisories/GHSA-4mpw-cpwj-hxxj (GitHub-reviewed advisory GHSA-4mpw-cpwj-hxxj lists affected ranges: NuGet microsoft.netcore.app.runtime.win-arm64 >=8.0.0 =11.0.0-preview.1 =9.0.0 =10.0.0 =8.0.0 =11.0.0-preview.1 =9.0.0 =10.0.0 =8.0.0 =11.0.0-preview.1 =9.0.0 =10.0.0 <=10.0.12)
- Verified: https://github.com/advisories/GHSA-4mpw-cpwj-hxxj (GitHub-reviewed advisory GHSA-4mpw-cpwj-hxxj lists affected ranges: NuGet microsoft.netcore.app.runtime.win-arm64 >=8.0.0 =11.0.0-preview.1 =9.0.0 =10.0.0 =8.0.0 =11.0.0-preview.1 =9.0.0 =10.0.0 =8.0.0 =11.0.0-preview.1 =9.0.0 =10.0.0 <10.0.14)
- Verified: https://osv.dev/vulnerability/GHSA-4mpw-cpwj-hxxj (OSV record GHSA-4mpw-cpwj-hxxj lists affected ranges: NuGet microsoft.netcore.app.runtime.win-arm64 >=8.0.0 =11.0.0-preview.1 =9.0.0 =10.0.0 =8.0.0 =11.0.0-preview.1 =9.0.0 =10.0.0 =8.0.0 =11.0.0-preview.1…)

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