Microsoft Security Advisory CVE-2026-62901 – .NET 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

EPSS

• CVE-2026-62901: 1.23% estimated exploitation activity in the next 30 days; percentile 69.01 (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.WebSockets. This advisory also provides guidance on what developers can do to update their applications to remove this vulnerability. An unchecked input for loop condition in .NET allows an unauthorized attacker to deny service over a network. Announcement Announcement for this issue can be found at https://github.com/dotnet/announcements/issues/428 CVSS Details - Version: 3.1 - Severity: High - Score: 7.5 - 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-606: Unchecked Input for Loop Condition Affected Platforms - Platforms: Windows, Linux, macOS - Architectures: All <a name="affected-packages"</aAffected Packages The vulnerability affects any Microsoft .NET project if it uses any of affected package versions listed below <a name=".NET 10"</a.NET 10 Package name | Affected version | Patched version ------------ |…

Published by the source

11 Aug 2026, 18:53 UTC

Last modified by the source

17 Aug 2026, 08:10 UTC

Source last checked

26 Oct 2026, 17:05 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-m93f-wj8c-rp8p

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-m93f-wj8c-rp8p

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2026-62901

Advisory: Microsoft Security Advisory CVE-2026-62901 – .NET Denial of Service Vulnerability
IDs: CVE-2026-62901, GHSA-m93f-wj8c-rp8p
Record: https://patchnext.com/advisories/cve-2026-62901 (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: 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.netcore.app.runtime.win-x86 10.0.11, 9.0.19, 8.0.30; microsoft.netcore.app.runtime.win-arm64 10.0.11, 9.0.19, 8.0.30; microsoft.netcore.app.runtime.linux-musl-x64 10.0.11, 9.0.19, 8.0.30; microsoft.netcore.app.runtime.linux-arm64 10.0.11, 9.0.19, 8.0.30; microsoft.netcore.app.runtime.linux-arm 10.0.11, 9.0.19, 8.0.30; microsoft.netcore.app.runtime.osx-x64 10.0.11, 9.0.19, 8.0.30; microsoft.netcore.app.runtime.linux-x64 10.0.11, 9.0.19, 8.0.30; microsoft.netcore.app.runtime.osx-arm64 10.0.11, 9.0.19, 8.0.30; microsoft.netcore.app.runtime.linux-musl-arm 10.0.11, 9.0.19, 8.0.30; microsoft.netcore.app.runtime.linux-musl-arm64 10.0.11, 9.0.19, 8.0.30; microsoft.netcore.app.runtime.win-x64 10.0.11, 9.0.19, 8.0.30. A vendor fix does not mean a deployment is fixed.

## Affected components
- NuGet microsoft.netcore.app.runtime.win-x86: affected >= 10.0.0, <= 10.0.10; >= 9.0.0, <= 9.0.18; >= 8.0.0, <= 8.0.29; fixed in 9.0.19, 10.0.11, 8.0.30
- NuGet microsoft.netcore.app.runtime.win-arm64: affected >= 10.0.0, <= 10.0.10; >= 9.0.0, <= 9.0.18; >= 8.0.0, <= 8.0.29; fixed in 9.0.19, 10.0.11, 8.0.30
- NuGet microsoft.netcore.app.runtime.linux-musl-x64: affected >= 10.0.0, <= 10.0.10; >= 9.0.0, <= 9.0.18; >= 8.0.0, <= 8.0.29; fixed in 9.0.19, 10.0.11, 8.0.30
- NuGet microsoft.netcore.app.runtime.linux-arm64: affected >= 10.0.0, <= 10.0.10; >= 9.0.0, <= 9.0.18; >= 8.0.0, <= 8.0.29; fixed in 9.0.19, 10.0.11, 8.0.30
- NuGet microsoft.netcore.app.runtime.linux-arm: affected >= 10.0.0, <= 10.0.10; >= 9.0.0, <= 9.0.18; >= 8.0.0, <= 8.0.29; fixed in 9.0.19, 10.0.11, 8.0.30
- NuGet microsoft.netcore.app.runtime.osx-x64: affected >= 10.0.0, <= 10.0.10; >= 9.0.0, <= 9.0.18; >= 8.0.0, <= 8.0.29; fixed in 9.0.19, 10.0.11, 8.0.30
- NuGet microsoft.netcore.app.runtime.linux-x64: affected >= 10.0.0, <= 10.0.10; >= 9.0.0, <= 9.0.18; >= 8.0.0, <= 8.0.29; fixed in 9.0.19, 10.0.11, 8.0.30
- NuGet microsoft.netcore.app.runtime.osx-arm64: affected >= 10.0.0, <= 10.0.10; >= 9.0.0, <= 9.0.18; >= 8.0.0, <= 8.0.29; fixed in 9.0.19, 10.0.11, 8.0.30
- NuGet microsoft.netcore.app.runtime.linux-musl-arm: affected >= 10.0.0, <= 10.0.10; >= 9.0.0, <= 9.0.18; >= 8.0.0, <= 8.0.29; fixed in 9.0.19, 10.0.11, 8.0.30
- NuGet microsoft.netcore.app.runtime.linux-musl-arm64: affected >= 10.0.0, <= 10.0.10; >= 9.0.0, <= 9.0.18; >= 8.0.0, <= 8.0.29; fixed in 9.0.19, 10.0.11, 8.0.30
- NuGet microsoft.netcore.app.runtime.win-x64: affected >= 10.0.0, <= 10.0.10; >= 9.0.0, <= 9.0.18; >= 8.0.0, <= 8.0.29; fixed in 9.0.19, 10.0.11, 8.0.30

## 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.linux-musl-x64: check the installed version with your package manager.
- NuGet microsoft.netcore.app.runtime.linux-arm64: check the installed version with your package manager.
- NuGet microsoft.netcore.app.runtime.linux-arm: check the installed version with your package manager.
- NuGet microsoft.netcore.app.runtime.osx-x64: check the installed version with your package manager.
- NuGet microsoft.netcore.app.runtime.linux-x64: check the installed version with your package manager.
- NuGet microsoft.netcore.app.runtime.osx-arm64: check the installed version with your package manager.
- NuGet microsoft.netcore.app.runtime.linux-musl-arm: check the installed version with your package manager.
- NuGet microsoft.netcore.app.runtime.linux-musl-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.linux-musl-x64, microsoft.netcore.app.runtime.linux-arm64, microsoft.netcore.app.runtime.linux-arm, microsoft.netcore.app.runtime.osx-x64, microsoft.netcore.app.runtime.linux-x64, microsoft.netcore.app.runtime.osx-arm64, microsoft.netcore.app.runtime.linux-musl-arm, microsoft.netcore.app.runtime.linux-musl-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-m93f-wj8c-rp8p (OSV record GHSA-m93f-wj8c-rp8p lists affected ranges: NuGet microsoft.netcore.app.runtime.win-arm64 >=10.0.0 =9.0.0 =8.0.0 =10.0.0 =9.0.0 =8.0.0 =10.0.0 =9.0.0 =8.0.0 =10.0.0 <10.0.11 (fixed),…)
- Verified: https://github.com/advisories/GHSA-m93f-wj8c-rp8p (GitHub-reviewed advisory GHSA-m93f-wj8c-rp8p lists affected ranges: NuGet microsoft.netcore.app.runtime.win-arm64 >=10.0.0 =9.0.0 =8.0.0 =10.0.0 =9.0.0 =8.0.0 =10.0.0 =9.0.0 =8.0.0 =10.0.0 =9.0.0 =8.0.0 <=8.0.29; NuGet…)

Commands are suggestions: review each one before running it.