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.NET
.NET NuGet
Not in CISA KEV
HIGH severity

.NET Core Elevation of Privilege VulnerabilityGHSA-rh58-r7jh-xhx3

HIGH

GHSA-rh58-r7jh-xhx3 is a high-severity (CVSS 7.5) vulnerability in Microsoft.NETCore.App.Runtime.win-x86. A fix is available for Microsoft.NETCore.App.Runtime.win-x86 — see the affected versions and patch details below.

Also known asBIT-dotnet-2021-26423BIT-dotnet-sdk-2021-26423CVE-2021-26423
Published
Updated
Affected
33 pkgs
Patched
33 / 33
Exploits
None indexed
Exploitation data as of Nov 6, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

  • CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
  • CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for GHSA-rh58-r7jh-xhx3.

EPSS Exploitation Probability

via FIRST.org ↗
3.9%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs90th percentile — riskier than 90% of all scored CVEsHighest risk
2.87%3.38%3.89%4.40%3.4%3.9%May 26Sep 26Nov 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

33 pkgs affected
.NETMicrosoft.NETCore.App.Runtime.win-x86.NETMicrosoft.NETCore.App.Runtime.win-x86.NETMicrosoft.NETCore.App.Runtime.win-x64.NETMicrosoft.NETCore.App.Runtime.win-x64.NETMicrosoft.NETCore.App.Runtime.win-arm64.NETMicrosoft.NETCore.App.Runtime.win-arm64.NETMicrosoft.NETCore.App.Runtime.win-arm.NETMicrosoft.NETCore.App.Runtime.win-arm+25 more

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects NuGet packages — download data is not available via public APIs for these ecosystems.

Description

Microsoft is releasing this security advisory to provide information about a vulnerability in .NET 5.0 and .NET Core 3.1. This advisory also provides guidance on what developers can do to update their applications to remove this vulnerability.

A denial of service vulnerability exists in .NET 5.0, .NET Core 3.1 and .NET Core 2.1 where .NET (Core) server applications providing WebSocket endpoints could be tricked into endlessly looping while trying to read a single WebSocket frame.

Patches

Other Details

Affected Packages

33 total 33 fixed
EcosystemPackageVulnerable rangeFix
.NETNuGetMicrosoft.NETCore.App.Runtime.win-x86≥ 3.1.0&&< 3.1.183.1.18dotnet add package Microsoft.NETCore.App.Runtime.win-x86 --version 3.1.18
.NETNuGetMicrosoft.NETCore.App.Runtime.win-x86≥ 5.0.0&&< 5.0.95.0.9dotnet add package Microsoft.NETCore.App.Runtime.win-x86 --version 5.0.9
.NETNuGetMicrosoft.NETCore.App.Runtime.win-x64≥ 3.1.0&&< 3.1.183.1.18dotnet add package Microsoft.NETCore.App.Runtime.win-x64 --version 3.1.18
.NETNuGetMicrosoft.NETCore.App.Runtime.win-x64≥ 5.0.0&&< 5.0.95.0.9dotnet add package Microsoft.NETCore.App.Runtime.win-x64 --version 5.0.9
.NETNuGetMicrosoft.NETCore.App.Runtime.win-arm64≥ 3.1.0&&< 3.1.183.1.18dotnet add package Microsoft.NETCore.App.Runtime.win-arm64 --version 3.1.18
.NETNuGetMicrosoft.NETCore.App.Runtime.win-arm64≥ 5.0.0&&< 5.0.95.0.9dotnet add package Microsoft.NETCore.App.Runtime.win-arm64 --version 5.0.9

Affected Products

5 products · 8 configurations
Application
.netmicrosoft
≥ 5.0 && ≤ 5.0.8
range
Application
.net coremicrosoft
≥ 3.1 && ≤ 3.1.17
range
Application
powershell coremicrosoft
≥ 7.1 && < 7.1.4
range
Application
visual studio 2017microsoft
≥ 15.0 && ≤ 15.9
range
Application
visual studio 2019microsoft
≥ 16.0 && ≤ 16.10
1 version
8.10

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for Microsoft.NETCore.App.Runtime.win-x86, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update Microsoft.NETCore.App.Runtime.win-x86 to 3.1.18 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-rh58-r7jh-xhx3 is resolved across your whole dependency graph.

  3. Workarounds

    Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatImportant
ProductFixed inAdvisory
.NET Core on Red Hat Enterprise Linuxrh-dotnet31-dotnet-0:3.1.118-1.el7_9RHSA-2021:3143
.NET Core on Red Hat Enterprise Linuxrh-dotnet50-dotnet-0:5.0.206-1.el7_9RHSA-2021:3147
Red Hat Enterprise Linux 8dotnet3.1-0:3.1.118-1.el8_4RHSA-2021:3142
Red Hat Enterprise Linux 8dotnet5.0-0:5.0.206-1.el8_4RHSA-2021:3148

Frequently Asked Questions

Microsoft is releasing this security advisory to provide information about a vulnerability in .NET 5.0 and .NET Core 3.1. This advisory also provides guidance on what developers can do to update their applications to remove this vulnerability. A denial of service vulnerability exists in .NET 5.0, .NET Core 3.1 and .NET Core 2.1 where .NET (Core) server applications providing WebSocket endpoints could be tricked into endlessly looping while trying to read a single WebSocket frame. ### Patches * If you're using .NET 5.0, you should download and install Runtime 5.0.9 or SDK 5.0.206 (for Visua
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.NET Core Elevation of Privilege Vulnerability (High 7.5)