GHSA-rh58-r7jh-xhx3 BIT-dotnet-2021-26423 BIT-dotnet-sdk-2021-26423 CVE-2021-26423
.NET Core Elevation of Privilege Vulnerability
- Severity
- 7.5 / 10
- High · CVSS 3.1
- Exploit chance (EPSS)
- 3.90%
- Chance of exploitation in the next 30 days. Higher than 90.27% of scored vulnerabilities.
- Known exploited
- No
- Not in CISA's catalog
- Weakness
- —
- Not classified
- Fix
- Available
- 23 packages have a fixed version
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
-
If you're using .NET 5.0, you should download and install Runtime 5.0.9 or SDK 5.0.206 (for Visual Studio 2019 v16.8) or SDK 5.0.303 (for Visual Studio 2019 V16.10) from https://dotnet.microsoft.com/download/dotnet-core/5.0.
-
If you're using .NET Core 3.1, you should download and install Runtime 3.1.18 or SDK 3.1.118 (for Visual Studio 2019 v16.4) or 3.1.412 (for Visual Studio 2019 v16.7 or later) from https://dotnet.microsoft.com/download/dotnet-core/3.1.
-
If you're using .NET Core 2.1, you should download and install Runtime 2.1.29 or SDK 2.1.525 (for Visual Studio 2019 v15.9) or 2.1.817 from https://dotnet.microsoft.com/download/dotnet-core/2.1.
Other Details
- Announcement for this issue can be found at https://github.com/dotnet/announcements/issues/194
- An Issue for this can be found at https://github.com/dotnet/runtime/issues/57175
- MSRC details for this can be found at https://msrc.microsoft.com/update-guide/en-US/vulnerability/CVE-2021-26423
Affected versions
NuGet
How to fix
Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.
Microsoft.NETCore.App.Runtime.Mono.LLVM.AOT.linux-arm64 NuGet → 5.0.9
- dotnet
dotnet add package Microsoft.NETCore.App.Runtime.Mono.LLVM.AOT.linux-arm64 --version 5.0.9
Microsoft.NETCore.App.Runtime.Mono.LLVM.AOT.linux-x64 NuGet → 5.0.9
- dotnet
dotnet add package Microsoft.NETCore.App.Runtime.Mono.LLVM.AOT.linux-x64 --version 5.0.9
Microsoft.NETCore.App.Runtime.Mono.LLVM.AOT.osx-x64 NuGet → 5.0.9
- dotnet
dotnet add package Microsoft.NETCore.App.Runtime.Mono.LLVM.AOT.osx-x64 --version 5.0.9
Microsoft.NETCore.App.Runtime.Mono.LLVM.linux-arm64 NuGet → 5.0.9
- dotnet
dotnet add package Microsoft.NETCore.App.Runtime.Mono.LLVM.linux-arm64 --version 5.0.9
Microsoft.NETCore.App.Runtime.Mono.LLVM.linux-x64 NuGet → 5.0.9
- dotnet
dotnet add package Microsoft.NETCore.App.Runtime.Mono.LLVM.linux-x64 --version 5.0.9
Microsoft.NETCore.App.Runtime.Mono.LLVM.osx-x64 NuGet → 5.0.9
- dotnet
dotnet add package Microsoft.NETCore.App.Runtime.Mono.LLVM.osx-x64 --version 5.0.9
Microsoft.NETCore.App.Runtime.Mono.linux-arm NuGet → 5.0.9
- dotnet
dotnet add package Microsoft.NETCore.App.Runtime.Mono.linux-arm --version 5.0.9
Microsoft.NETCore.App.Runtime.Mono.linux-arm64 NuGet → 5.0.9
- dotnet
dotnet add package Microsoft.NETCore.App.Runtime.Mono.linux-arm64 --version 5.0.9
Microsoft.NETCore.App.Runtime.Mono.linux-musl-x64 NuGet → 5.0.9
- dotnet
dotnet add package Microsoft.NETCore.App.Runtime.Mono.linux-musl-x64 --version 5.0.9
Microsoft.NETCore.App.Runtime.Mono.linux-x64 NuGet → 5.0.9
- dotnet
dotnet add package Microsoft.NETCore.App.Runtime.Mono.linux-x64 --version 5.0.9
Microsoft.NETCore.App.Runtime.Mono.osx-x64 NuGet → 5.0.9
- dotnet
dotnet add package Microsoft.NETCore.App.Runtime.Mono.osx-x64 --version 5.0.9
Microsoft.NETCore.App.Runtime.linux-arm NuGet → 3.1.18
- dotnet
dotnet add package Microsoft.NETCore.App.Runtime.linux-arm --version 3.1.18
Microsoft.NETCore.App.Runtime.linux-arm64 NuGet → 3.1.18
- dotnet
dotnet add package Microsoft.NETCore.App.Runtime.linux-arm64 --version 3.1.18
Microsoft.NETCore.App.Runtime.linux-musl-arm NuGet → 5.0.9
- dotnet
dotnet add package Microsoft.NETCore.App.Runtime.linux-musl-arm --version 5.0.9
Microsoft.NETCore.App.Runtime.linux-musl-arm64 NuGet → 3.1.18
- dotnet
dotnet add package Microsoft.NETCore.App.Runtime.linux-musl-arm64 --version 3.1.18
Microsoft.NETCore.App.Runtime.linux-musl-x64 NuGet → 3.1.18
- dotnet
dotnet add package Microsoft.NETCore.App.Runtime.linux-musl-x64 --version 3.1.18
Microsoft.NETCore.App.Runtime.linux-x64 NuGet → 3.1.18
- dotnet
dotnet add package Microsoft.NETCore.App.Runtime.linux-x64 --version 3.1.18
Microsoft.NETCore.App.Runtime.osx-x64 NuGet → 3.1.18
- dotnet
dotnet add package Microsoft.NETCore.App.Runtime.osx-x64 --version 3.1.18
Microsoft.NETCore.App.Runtime.rhel.6-x64 NuGet → 3.1.18
- dotnet
dotnet add package Microsoft.NETCore.App.Runtime.rhel.6-x64 --version 3.1.18
Microsoft.NETCore.App.Runtime.win-arm NuGet → 3.1.18
- dotnet
dotnet add package Microsoft.NETCore.App.Runtime.win-arm --version 3.1.18
Microsoft.NETCore.App.Runtime.win-arm64 NuGet → 3.1.18
- dotnet
dotnet add package Microsoft.NETCore.App.Runtime.win-arm64 --version 3.1.18
Microsoft.NETCore.App.Runtime.win-x64 NuGet → 3.1.18
- dotnet
dotnet add package Microsoft.NETCore.App.Runtime.win-x64 --version 3.1.18
Microsoft.NETCore.App.Runtime.win-x86 NuGet → 3.1.18
- dotnet
dotnet add package Microsoft.NETCore.App.Runtime.win-x86 --version 3.1.18
Severity breakdown
CVSS 3.1 7.5
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
References
Advisories
Other links
Timeline
- Published
- Last updated by the source
- Latest EPSS score
Related advisories
| Advisory | Severity | Why it's related |
|---|---|---|
| CVE-2020-1147 .NET Framework, SharePoint Server, and Visual Studio Remote Code Execution Vulnerability | High Known exploited | Also affects Microsoft.NETCore.App.Runtime.linux-arm64 |
| GHSA-87vj-4hqv-22p9 Microsoft Security Advisory CVE-2026-96233 - .NET and Visual Studio Denial of Service Vulnerability | High | Also affects Microsoft.NETCore.App.Runtime.linux-arm64 |
| GHSA-2j93-m82w-73j2 Microsoft Security Advisory CVE-2026-96231 - .NET and Visual Studio Elevation of Privilege Vulnerability | High | Also affects Microsoft.NETCore.App.Runtime.linux-arm64 |
| GHSA-w6wh-p4g7-mpj2 Microsoft Security Advisory CVE-2026-96225 - .NET and Visual Studio Elevation of Privilege Vulnerability | High | Also affects Microsoft.NETCore.App.Runtime.linux-arm64 |
| GHSA-4mpw-cpwj-hxxj Microsoft Security Advisory CVE-2026-70197 - .NET and Visual Studio Remote Code Execution Vulnerability | High | Also affects Microsoft.NETCore.App.Runtime.win-arm64 |
| GHSA-fqpq-cx42-9jmm Microsoft Security Advisory CVE-2026-70194 - .NET and Visual Studio Security Feature Bypass Vulnerability | Medium | Also affects Microsoft.NETCore.App.Runtime.linux-arm64 |
| GHSA-3rxq-g8rj-r2cf Microsoft Security Advisory CVE-2026-69651 - .NET and Visual Studio Denial of Service Vulnerability | High | Also affects Microsoft.NETCore.App.Runtime.linux-arm64 |
| GHSA-wxxw-5cvc-53j7 Microsoft Security Advisory CVE-2026-66822 - .NET and Visual Studio Information Disclosure Vulnerability | Medium | Also affects Microsoft.NETCore.App.Runtime.linux-arm64 |
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