CVE-2021-26423

HIGH

.NET Core Elevation of Privilege Vulnerability

Published October 25, 2022Updated December 1, 2024Source: osv

Summary

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

Remediation

Upgrade to the fixed version using your package manager.

NuGet

Update Microsoft.NETCore.App.Runtime.linux-arm64 to 3.1.18 or later

dotnet add package Microsoft.NETCore.App.Runtime.linux-arm64 --version 3.1.18

NuGet

Update Microsoft.NETCore.App.Runtime.Mono.linux-arm64 to 5.0.9 or later

dotnet add package Microsoft.NETCore.App.Runtime.Mono.linux-arm64 --version 5.0.9

NuGet

Update Microsoft.NETCore.App.Runtime.Mono.linux-arm to 5.0.9 or later

dotnet add package Microsoft.NETCore.App.Runtime.Mono.linux-arm --version 5.0.9

NuGet

Update Microsoft.NETCore.App.Runtime.linux-musl-x64 to 5.0.9 or later

dotnet add package Microsoft.NETCore.App.Runtime.linux-musl-x64 --version 5.0.9

NuGet

Update Microsoft.NETCore.App.Runtime.linux-arm to 5.0.9 or later

dotnet add package Microsoft.NETCore.App.Runtime.linux-arm --version 5.0.9

NuGet

Update Microsoft.NETCore.App.Runtime.osx-x64 to 3.1.18 or later

dotnet add package Microsoft.NETCore.App.Runtime.osx-x64 --version 3.1.18

NuGet

Update Microsoft.NETCore.App.Runtime.Mono.LLVM.osx-x64 to 5.0.9 or later

dotnet add package Microsoft.NETCore.App.Runtime.Mono.LLVM.osx-x64 --version 5.0.9

NuGet

Update Microsoft.NETCore.App.Runtime.Mono.LLVM.linux-x64 to 5.0.9 or later

dotnet add package Microsoft.NETCore.App.Runtime.Mono.LLVM.linux-x64 --version 5.0.9

NuGet

Update Microsoft.NETCore.App.Runtime.win-arm to 5.0.9 or later

dotnet add package Microsoft.NETCore.App.Runtime.win-arm --version 5.0.9

NuGet

Update Microsoft.NETCore.App.Runtime.linux-musl-x64 to 3.1.18 or later

dotnet add package Microsoft.NETCore.App.Runtime.linux-musl-x64 --version 3.1.18

NuGet

Update Microsoft.NETCore.App.Runtime.linux-musl-arm to 5.0.9 or later

dotnet add package Microsoft.NETCore.App.Runtime.linux-musl-arm --version 5.0.9

NuGet

Update Microsoft.NETCore.App.Runtime.win-x64 to 5.0.9 or later

dotnet add package Microsoft.NETCore.App.Runtime.win-x64 --version 5.0.9

NuGet

Update Microsoft.NETCore.App.Runtime.win-x64 to 3.1.18 or later

dotnet add package Microsoft.NETCore.App.Runtime.win-x64 --version 3.1.18

NuGet

Update Microsoft.NETCore.App.Runtime.linux-musl-arm64 to 5.0.9 or later

dotnet add package Microsoft.NETCore.App.Runtime.linux-musl-arm64 --version 5.0.9

NuGet

Update Microsoft.NETCore.App.Runtime.Mono.linux-musl-x64 to 5.0.9 or later

dotnet add package Microsoft.NETCore.App.Runtime.Mono.linux-musl-x64 --version 5.0.9

NuGet

Update Microsoft.NETCore.App.Runtime.Mono.LLVM.AOT.linux-x64 to 5.0.9 or later

dotnet add package Microsoft.NETCore.App.Runtime.Mono.LLVM.AOT.linux-x64 --version 5.0.9

NuGet

Update Microsoft.NETCore.App.Runtime.win-arm64 to 5.0.9 or later

dotnet add package Microsoft.NETCore.App.Runtime.win-arm64 --version 5.0.9

NuGet

Update Microsoft.NETCore.App.Runtime.win-x86 to 3.1.18 or later

dotnet add package Microsoft.NETCore.App.Runtime.win-x86 --version 3.1.18

NuGet

Update Microsoft.NETCore.App.Runtime.Mono.LLVM.AOT.osx-x64 to 5.0.9 or later

dotnet add package Microsoft.NETCore.App.Runtime.Mono.LLVM.AOT.osx-x64 --version 5.0.9

NuGet

Update Microsoft.NETCore.App.Runtime.linux-x64 to 3.1.18 or later

dotnet add package Microsoft.NETCore.App.Runtime.linux-x64 --version 3.1.18

NuGet

Update Microsoft.NETCore.App.Runtime.Mono.linux-x64 to 5.0.9 or later

dotnet add package Microsoft.NETCore.App.Runtime.Mono.linux-x64 --version 5.0.9

NuGet

Update Microsoft.NETCore.App.Runtime.linux-x64 to 5.0.9 or later

dotnet add package Microsoft.NETCore.App.Runtime.linux-x64 --version 5.0.9

NuGet

Update Microsoft.NETCore.App.Runtime.linux-musl-arm64 to 3.1.18 or later

dotnet add package Microsoft.NETCore.App.Runtime.linux-musl-arm64 --version 3.1.18

NuGet

Update Microsoft.NETCore.App.Runtime.win-arm64 to 3.1.18 or later

dotnet add package Microsoft.NETCore.App.Runtime.win-arm64 --version 3.1.18

NuGet

Update Microsoft.NETCore.App.Runtime.linux-arm to 3.1.18 or later

dotnet add package Microsoft.NETCore.App.Runtime.linux-arm --version 3.1.18

NuGet

Update Microsoft.NETCore.App.Runtime.rhel.6-x64 to 3.1.18 or later

dotnet add package Microsoft.NETCore.App.Runtime.rhel.6-x64 --version 3.1.18

NuGet

Update Microsoft.NETCore.App.Runtime.win-x86 to 5.0.9 or later

dotnet add package Microsoft.NETCore.App.Runtime.win-x86 --version 5.0.9

NuGet

Update Microsoft.NETCore.App.Runtime.Mono.LLVM.AOT.linux-arm64 to 5.0.9 or later

dotnet add package Microsoft.NETCore.App.Runtime.Mono.LLVM.AOT.linux-arm64 --version 5.0.9

NuGet

Update Microsoft.NETCore.App.Runtime.osx-x64 to 5.0.9 or later

dotnet add package Microsoft.NETCore.App.Runtime.osx-x64 --version 5.0.9

NuGet

Update Microsoft.NETCore.App.Runtime.linux-arm64 to 5.0.9 or later

dotnet add package Microsoft.NETCore.App.Runtime.linux-arm64 --version 5.0.9

NuGet

Update Microsoft.NETCore.App.Runtime.win-arm to 3.1.18 or later

dotnet add package Microsoft.NETCore.App.Runtime.win-arm --version 3.1.18

NuGet

Update Microsoft.NETCore.App.Runtime.Mono.LLVM.linux-arm64 to 5.0.9 or later

dotnet add package Microsoft.NETCore.App.Runtime.Mono.LLVM.linux-arm64 --version 5.0.9

NuGet

Update Microsoft.NETCore.App.Runtime.Mono.osx-x64 to 5.0.9 or later

dotnet add package Microsoft.NETCore.App.Runtime.Mono.osx-x64 --version 5.0.9

After upgrading, run your dependency scanner again to confirm the vulnerability is resolved.

Affected Packages (33)

Package	Ecosystem	Affected	Fixed In
Microsoft.NETCore.App.Runtime.linux-arm64	nuget	3.1.0, 3.1.1, 3.1.10, 3.1.11 (+14 more)	3.1.18
Microsoft.NETCore.App.Runtime.Mono.linux-arm64	nuget	5.0.0, 5.0.1, 5.0.2, 5.0.3 (+5 more)	5.0.9
Microsoft.NETCore.App.Runtime.Mono.linux-arm	nuget	5.0.0, 5.0.1, 5.0.2, 5.0.3 (+5 more)	5.0.9
Microsoft.NETCore.App.Runtime.linux-musl-x64	nuget	5.0.0, 5.0.1, 5.0.2, 5.0.3 (+5 more)	5.0.9
Microsoft.NETCore.App.Runtime.linux-arm	nuget	5.0.0, 5.0.1, 5.0.2, 5.0.3 (+5 more)	5.0.9
Microsoft.NETCore.App.Runtime.osx-x64	nuget	3.1.0, 3.1.1, 3.1.10, 3.1.11 (+14 more)	3.1.18
Microsoft.NETCore.App.Runtime.Mono.LLVM.osx-x64	nuget	5.0.0, 5.0.1, 5.0.2, 5.0.3 (+5 more)	5.0.9
Microsoft.NETCore.App.Runtime.Mono.LLVM.linux-x64	nuget	5.0.0, 5.0.1, 5.0.2, 5.0.3 (+5 more)	5.0.9
Microsoft.NETCore.App.Runtime.win-arm	nuget	5.0.0, 5.0.1, 5.0.2, 5.0.3 (+5 more)	5.0.9
Microsoft.NETCore.App.Runtime.linux-musl-x64	nuget	3.1.0, 3.1.1, 3.1.10, 3.1.11 (+14 more)	3.1.18
Microsoft.NETCore.App.Runtime.linux-musl-arm	nuget	5.0.0, 5.0.1, 5.0.2, 5.0.3 (+5 more)	5.0.9
Microsoft.NETCore.App.Runtime.win-x64	nuget	5.0.0, 5.0.1, 5.0.2, 5.0.3 (+5 more)	5.0.9
Microsoft.NETCore.App.Runtime.win-x64	nuget	3.1.0, 3.1.1, 3.1.10, 3.1.11 (+14 more)	3.1.18
Microsoft.NETCore.App.Runtime.linux-musl-arm64	nuget	5.0.0, 5.0.1, 5.0.2, 5.0.3 (+5 more)	5.0.9
Microsoft.NETCore.App.Runtime.Mono.linux-musl-x64	nuget	5.0.0, 5.0.1, 5.0.2, 5.0.3 (+5 more)	5.0.9
Microsoft.NETCore.App.Runtime.Mono.LLVM.AOT.linux-x64	nuget	5.0.0, 5.0.1, 5.0.2, 5.0.3 (+5 more)	5.0.9
Microsoft.NETCore.App.Runtime.win-arm64	nuget	5.0.0, 5.0.1, 5.0.2, 5.0.3 (+5 more)	5.0.9
Microsoft.NETCore.App.Runtime.win-x86	nuget	3.1.0, 3.1.1, 3.1.10, 3.1.11 (+14 more)	3.1.18
Microsoft.NETCore.App.Runtime.Mono.LLVM.AOT.osx-x64	nuget	5.0.0, 5.0.1, 5.0.2, 5.0.3 (+5 more)	5.0.9
Microsoft.NETCore.App.Runtime.linux-x64	nuget	3.1.0, 3.1.1, 3.1.10, 3.1.11 (+14 more)	3.1.18
Microsoft.NETCore.App.Runtime.Mono.linux-x64	nuget	5.0.0, 5.0.1, 5.0.2, 5.0.3 (+5 more)	5.0.9
Microsoft.NETCore.App.Runtime.linux-x64	nuget	5.0.0, 5.0.1, 5.0.2, 5.0.3 (+5 more)	5.0.9
Microsoft.NETCore.App.Runtime.linux-musl-arm64	nuget	3.1.0, 3.1.1, 3.1.10, 3.1.11 (+14 more)	3.1.18
Microsoft.NETCore.App.Runtime.win-arm64	nuget	3.1.0, 3.1.1, 3.1.10, 3.1.11 (+14 more)	3.1.18
Microsoft.NETCore.App.Runtime.linux-arm	nuget	3.1.0, 3.1.1, 3.1.10, 3.1.11 (+14 more)	3.1.18
Microsoft.NETCore.App.Runtime.rhel.6-x64	nuget	3.1.0, 3.1.1, 3.1.10, 3.1.11 (+14 more)	3.1.18
Microsoft.NETCore.App.Runtime.win-x86	nuget	5.0.0, 5.0.1, 5.0.2, 5.0.3 (+5 more)	5.0.9
Microsoft.NETCore.App.Runtime.Mono.LLVM.AOT.linux-arm64	nuget	5.0.0, 5.0.1, 5.0.2, 5.0.3 (+5 more)	5.0.9
Microsoft.NETCore.App.Runtime.osx-x64	nuget	5.0.0, 5.0.1, 5.0.2, 5.0.3 (+5 more)	5.0.9
Microsoft.NETCore.App.Runtime.linux-arm64	nuget	5.0.0, 5.0.1, 5.0.2, 5.0.3 (+5 more)	5.0.9
Microsoft.NETCore.App.Runtime.win-arm	nuget	3.1.0, 3.1.1, 3.1.10, 3.1.11 (+14 more)	3.1.18
Microsoft.NETCore.App.Runtime.Mono.LLVM.linux-arm64	nuget	5.0.0, 5.0.1, 5.0.2, 5.0.3 (+5 more)	5.0.9
Microsoft.NETCore.App.Runtime.Mono.osx-x64	nuget	5.0.0, 5.0.1, 5.0.2, 5.0.3 (+5 more)	5.0.9

CVSS Score Breakdown

What the CVSS (Common Vulnerability Scoring System) 7.5 score means for each attack dimension.

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

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

References

Frequently Asked Questions

What is CVE-2021-26423?: .NET Core Elevation of Privilege Vulnerability This vulnerability has been assigned a severity rating of HIGH (CVSS score: 7.5/10).
How do I check if my project is affected by CVE-2021-26423?: CVE-2021-26423 affects Microsoft.NETCore.App.Runtime.linux-arm64, Microsoft.NETCore.App.Runtime.Mono.linux-arm64 and Microsoft.NETCore.App.Runtime.Mono.linux-arm (and 20 more). Use GeekWala's free vulnerability scanner to check your dependencies against CVE-2021-26423 and 200,000+ other known vulnerabilities.

Severity & Exploitability

CVSS Score

7.5

High exploitability or significant impact. Prioritize remediation within days.

Also Known As

GHSA-rh58-r7jh-xhx3

BIT-dotnet-2021-26423

BIT-dotnet-sdk-2021-26423

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