CVE-2021-31957

ASP.NET Core Denial of Service Vulnerability

5.9 MediumFix available

ASP.NET Core Denial of Service Vulnerability

Attack profile

How easy it is to exploit

Attack vector: Network
Complexity: High
Privileges needed: None
User interaction: None

What an attacker can affect

Confidentiality: None
Integrity: None
Availability: High

Exploit likelihood

5.14%Up 4.6 points since Jun 9, 2021

What each source reports

CVE List Score used 5.9

ASP.NET Core Denial of Service Vulnerability

ASP.NET Core Denial of Service Vulnerability

Record: CVE-2021-31957
CVSS 3.1: 5.9 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H/E:U/RL:O/RC:C
Weakness: CWE-400
Updated: 2026-11-02

EUVDEUVD-2021-2231 5.9

ASP.NET Core Denial of Service Vulnerability

Record: EUVD-2021-2231
CVSS 3.1: 5.9 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H/E:U/RL:O/RC:C
Updated: 2026-11-02

GitHub AdvisoriesGHSA-mcwm-2wmc-6hv4 7.5

ASP.NET Core Denial of Service Vulnerability

Withdrawn

This advisory was initially published and mapped incorrectly to nuget Microsoft.NETCore.App.Ref. We later reanalyzed this advisory and found it does not have a direct mapping to a NuGet package. Thus we have withdrawn this advisory.

The underlying ASP.NET Core Denial of Service Vulnerability and CVE-2021-31957 remain legitimate.

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 when ASP.NET Core improperly handles client disconnect. An attacker who successfully exploited this vulnerability could cause a denial of service against an ASP.NET Core web application. The vulnerability can be exploited remotely, without authentication.

Patches

If you're using .NET 5.0, you should download and install Runtime 5.0.7 or SDK 5.0.204 (for Visual Studio 2019 v16.8) or SDK 5.0.301 (for Visual Studio 2019 16.10) from https://dotnet.microsoft.com/download/dotnet-core/5.0.
If you're using .NET Core 3.1, you should download and install Runtime 3.1.16 or SDK 3.1.116 (for Visual Studio 2019 v16.4) or 3.1.410 (for Visual Studio 2019 v16.5 or later) from https://dotnet.microsoft.com/download/dotnet-core/3.1.

Other Details

Announcement for this issue can be found at https://github.com/dotnet/announcements/issues/188
An Issue for this can be found at https://github.com/dotnet/aspnetcore/issues/33369
MSRC details for this can be found at https://msrc.microsoft.com/update-guide/en-US/vulnerability/CVE-2021-31957

Record: GHSA-mcwm-2wmc-6hv4
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated: 2026-11-02

NVD 5.9

ASP.NET Core Denial of Service Vulnerability

Record: CVE-2021-31957
CVSS 3.1: 5.9 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CVSS 2.0: 5.0 MediumAV:N/AC:L/Au:N/C:N/I:N/A:P
Weakness: CWE-400
Updated: 2026-11-02

OSV 5.9

ASP.NET Core Denial of Service Vulnerability

Record: CVE-2021-31957
CVSS 3.1: 5.9 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated: 2026-11-02

OSVGHSA-mcwm-2wmc-6hv4 7.5

ASP.NET Core Denial of Service Vulnerability

Withdrawn

The underlying ASP.NET Core Denial of Service Vulnerability and CVE-2021-31957 remain legitimate.

Description.

Patches

If you're using .NET 5.0, you should download and install Runtime 5.0.7 or SDK 5.0.204 (for Visual Studio 2019 v16.8) or SDK 5.0.301 (for Visual Studio 2019 16.10) from https://dotnet.microsoft.com/download/dotnet-core/5.0.
If you're using .NET Core 3.1, you should download and install Runtime 3.1.16 or SDK 3.1.116 (for Visual Studio 2019 v16.4) or 3.1.410 (for Visual Studio 2019 v16.5 or later) from https://dotnet.microsoft.com/download/dotnet-core/3.1.

Other Details

Announcement for this issue can be found at https://github.com/dotnet/announcements/issues/188
An Issue for this can be found at https://github.com/dotnet/aspnetcore/issues/33369
MSRC details for this can be found at https://msrc.microsoft.com/update-guide/en-US/vulnerability/CVE-2021-31957

Record: GHSA-mcwm-2wmc-6hv4
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated: 2026-11-02

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OSVRHSA-2021:2350 5.9

Red Hat Security Advisory: .NET Core 3.1 on RHEL 7 security and bugfix update

Record: RHSA-2021:2350
CVSS 3.1: 5.9 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated: 2026-11-02

OSVRHSA-2021:2351 5.9

Red Hat Security Advisory: .NET 5.0 on RHEL 7 security and bugfix update

Record: RHSA-2021:2351
CVSS 3.1: 5.9 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated: 2026-11-02

OSVRHSA-2021:2352 5.9

Red Hat Security Advisory: .NET Core 3.1 security and bugfix update

Record: RHSA-2021:2352
CVSS 3.1: 5.9 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated: 2026-11-02

OSVRHSA-2021:2353 5.9

Red Hat Security Advisory: .NET 5.0 security and bugfix update

Record: RHSA-2021:2353
CVSS 3.1: 5.9 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated: 2026-11-02

OSVBIT-dotnet-2021-31957 No score

ASP.NET Core Denial of Service Vulnerability

ASP.NET Core Denial of Service Vulnerability

Record: BIT-dotnet-2021-31957
Updated: 2026-11-02

OSVBIT-dotnet-sdk-2021-31957 No score

ASP.NET Core Denial of Service Vulnerability

ASP.NET Core Denial of Service Vulnerability

Record: BIT-dotnet-sdk-2021-31957
Updated: 2026-11-02

Affected products

Affected packages

Affected packages
Package	Affected	Fixed
`dotnet` Bitnami	5.0.0 up to 5.0.7	5.0.7
`dotnet-sdk` Bitnami	5.0.0 up to 5.0.7	5.0.7
`rh-dotnet31-aspnetcore-runtime-3.1` Red Hat:rhel_dotnet:3.1::el7	before 0:3.1.16-1.el7_9	0:3.1.16-1.el7_9
`rh-dotnet31-aspnetcore-targeting-pack-3.1` Red Hat:rhel_dotnet:3.1::el7	before 0:3.1.16-1.el7_9	0:3.1.16-1.el7_9
`rh-dotnet31-dotnet` Red Hat:rhel_dotnet:3.1::el7	before 0:3.1.116-1.el7_9	0:3.1.116-1.el7_9
`rh-dotnet31-dotnet-apphost-pack-3.1` Red Hat:rhel_dotnet:3.1::el7	before 0:3.1.16-1.el7_9	0:3.1.16-1.el7_9
`rh-dotnet31-dotnet-debuginfo` Red Hat:rhel_dotnet:3.1::el7	before 0:3.1.116-1.el7_9	0:3.1.116-1.el7_9
`rh-dotnet31-dotnet-host` Red Hat:rhel_dotnet:3.1::el7	before 0:3.1.16-1.el7_9	0:3.1.16-1.el7_9
`rh-dotnet31-dotnet-hostfxr-3.1` Red Hat:rhel_dotnet:3.1::el7	before 0:3.1.16-1.el7_9	0:3.1.16-1.el7_9
`rh-dotnet31-dotnet-runtime-3.1` Red Hat:rhel_dotnet:3.1::el7	before 0:3.1.16-1.el7_9	0:3.1.16-1.el7_9

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Affected packages
Package	Affected	Fixed
`rh-dotnet31-dotnet-sdk-3.1` Red Hat:rhel_dotnet:3.1::el7	before 0:3.1.116-1.el7_9	0:3.1.116-1.el7_9
`rh-dotnet31-dotnet-targeting-pack-3.1` Red Hat:rhel_dotnet:3.1::el7	before 0:3.1.16-1.el7_9	0:3.1.16-1.el7_9
`rh-dotnet31-dotnet-templates-3.1` Red Hat:rhel_dotnet:3.1::el7	before 0:3.1.116-1.el7_9	0:3.1.116-1.el7_9
`rh-dotnet31-netstandard-targeting-pack-2.1` Red Hat:rhel_dotnet:3.1::el7	before 0:3.1.116-1.el7_9	0:3.1.116-1.el7_9
`rh-dotnet50-aspnetcore-runtime-5.0` Red Hat:rhel_dotnet:5.0::el7	before 0:5.0.7-1.el7_9	0:5.0.7-1.el7_9
`rh-dotnet50-aspnetcore-targeting-pack-5.0` Red Hat:rhel_dotnet:5.0::el7	before 0:5.0.7-1.el7_9	0:5.0.7-1.el7_9
`rh-dotnet50-dotnet` Red Hat:rhel_dotnet:5.0::el7	before 0:5.0.204-1.el7_9	0:5.0.204-1.el7_9
`rh-dotnet50-dotnet-apphost-pack-5.0` Red Hat:rhel_dotnet:5.0::el7	before 0:5.0.7-1.el7_9	0:5.0.7-1.el7_9
`rh-dotnet50-dotnet-debuginfo` Red Hat:rhel_dotnet:5.0::el7	before 0:5.0.204-1.el7_9	0:5.0.204-1.el7_9
`rh-dotnet50-dotnet-host` Red Hat:rhel_dotnet:5.0::el7	before 0:5.0.7-1.el7_9	0:5.0.7-1.el7_9
`rh-dotnet50-dotnet-hostfxr-5.0` Red Hat:rhel_dotnet:5.0::el7	before 0:5.0.7-1.el7_9	0:5.0.7-1.el7_9
`rh-dotnet50-dotnet-runtime-5.0` Red Hat:rhel_dotnet:5.0::el7	before 0:5.0.7-1.el7_9	0:5.0.7-1.el7_9
`rh-dotnet50-dotnet-sdk-5.0` Red Hat:rhel_dotnet:5.0::el7	before 0:5.0.204-1.el7_9	0:5.0.204-1.el7_9
`rh-dotnet50-dotnet-targeting-pack-5.0` Red Hat:rhel_dotnet:5.0::el7	before 0:5.0.7-1.el7_9	0:5.0.7-1.el7_9
`rh-dotnet50-dotnet-templates-5.0` Red Hat:rhel_dotnet:5.0::el7	before 0:5.0.204-1.el7_9	0:5.0.204-1.el7_9
`rh-dotnet50-netstandard-targeting-pack-2.1` Red Hat:rhel_dotnet:5.0::el7	before 0:5.0.204-1.el7_9	0:5.0.204-1.el7_9
`aspnetcore-runtime-3.1` Red Hat:enterprise_linux:8::appstream	before 0:3.1.16-1.el8_4	0:3.1.16-1.el8_4
`aspnetcore-targeting-pack-3.1` Red Hat:enterprise_linux:8::appstream	before 0:3.1.16-1.el8_4	0:3.1.16-1.el8_4
`dotnet-apphost-pack-3.1` Red Hat:enterprise_linux:8::appstream	before 0:3.1.16-1.el8_4	0:3.1.16-1.el8_4
`dotnet-apphost-pack-3.1-debuginfo` Red Hat:enterprise_linux:8::appstream	before 0:3.1.16-1.el8_4	0:3.1.16-1.el8_4
`dotnet-hostfxr-3.1` Red Hat:enterprise_linux:8::appstream	before 0:3.1.16-1.el8_4	0:3.1.16-1.el8_4
`dotnet-hostfxr-3.1-debuginfo` Red Hat:enterprise_linux:8::appstream	before 0:3.1.16-1.el8_4	0:3.1.16-1.el8_4
`dotnet-runtime-3.1` Red Hat:enterprise_linux:8::appstream	before 0:3.1.16-1.el8_4	0:3.1.16-1.el8_4
`dotnet-runtime-3.1-debuginfo` Red Hat:enterprise_linux:8::appstream	before 0:3.1.16-1.el8_4	0:3.1.16-1.el8_4
`dotnet-sdk-3.1` Red Hat:enterprise_linux:8::appstream	before 0:3.1.116-1.el8_4	0:3.1.116-1.el8_4
`dotnet-sdk-3.1-debuginfo` Red Hat:enterprise_linux:8::appstream	before 0:3.1.116-1.el8_4	0:3.1.116-1.el8_4
`dotnet-targeting-pack-3.1` Red Hat:enterprise_linux:8::appstream	before 0:3.1.16-1.el8_4	0:3.1.16-1.el8_4
`dotnet-templates-3.1` Red Hat:enterprise_linux:8::appstream	before 0:3.1.116-1.el8_4	0:3.1.116-1.el8_4
`dotnet3.1` Red Hat:enterprise_linux:8::appstream	before 0:3.1.116-1.el8_4	0:3.1.116-1.el8_4
`dotnet3.1-debuginfo` Red Hat:enterprise_linux:8::appstream	before 0:3.1.116-1.el8_4	0:3.1.116-1.el8_4
`dotnet3.1-debugsource` Red Hat:enterprise_linux:8::appstream	before 0:3.1.116-1.el8_4	0:3.1.116-1.el8_4
`aspnetcore-runtime-5.0` Red Hat:enterprise_linux:8::appstream	before 0:5.0.7-1.el8_4	0:5.0.7-1.el8_4
`aspnetcore-targeting-pack-5.0` Red Hat:enterprise_linux:8::appstream	before 0:5.0.7-1.el8_4	0:5.0.7-1.el8_4
`dotnet` Red Hat:enterprise_linux:8::appstream	before 0:5.0.204-1.el8_4	0:5.0.204-1.el8_4
`dotnet-apphost-pack-5.0` Red Hat:enterprise_linux:8::appstream	before 0:5.0.7-1.el8_4	0:5.0.7-1.el8_4
`dotnet-apphost-pack-5.0-debuginfo` Red Hat:enterprise_linux:8::appstream	before 0:5.0.7-1.el8_4	0:5.0.7-1.el8_4
`dotnet-host` Red Hat:enterprise_linux:8::appstream	before 0:5.0.7-1.el8_4	0:5.0.7-1.el8_4
`dotnet-host-debuginfo` Red Hat:enterprise_linux:8::appstream	before 0:5.0.7-1.el8_4	0:5.0.7-1.el8_4
`dotnet-hostfxr-5.0` Red Hat:enterprise_linux:8::appstream	before 0:5.0.7-1.el8_4	0:5.0.7-1.el8_4
`dotnet-hostfxr-5.0-debuginfo` Red Hat:enterprise_linux:8::appstream	before 0:5.0.7-1.el8_4	0:5.0.7-1.el8_4
`dotnet-runtime-5.0` Red Hat:enterprise_linux:8::appstream	before 0:5.0.7-1.el8_4	0:5.0.7-1.el8_4
`dotnet-runtime-5.0-debuginfo` Red Hat:enterprise_linux:8::appstream	before 0:5.0.7-1.el8_4	0:5.0.7-1.el8_4
`dotnet-sdk-5.0` Red Hat:enterprise_linux:8::appstream	before 0:5.0.204-1.el8_4	0:5.0.204-1.el8_4
`dotnet-sdk-5.0-debuginfo` Red Hat:enterprise_linux:8::appstream	before 0:5.0.204-1.el8_4	0:5.0.204-1.el8_4
`dotnet-targeting-pack-5.0` Red Hat:enterprise_linux:8::appstream	before 0:5.0.7-1.el8_4	0:5.0.7-1.el8_4
`dotnet-templates-5.0` Red Hat:enterprise_linux:8::appstream	before 0:5.0.204-1.el8_4	0:5.0.204-1.el8_4
`dotnet5.0` Red Hat:enterprise_linux:8::appstream	before 0:5.0.204-1.el8_4	0:5.0.204-1.el8_4
`dotnet5.0-debuginfo` Red Hat:enterprise_linux:8::appstream	before 0:5.0.204-1.el8_4	0:5.0.204-1.el8_4
`dotnet5.0-debugsource` Red Hat:enterprise_linux:8::appstream	before 0:5.0.204-1.el8_4	0:5.0.204-1.el8_4
`netstandard-targeting-pack-2.1` Red Hat:enterprise_linux:8::appstream	before 0:5.0.204-1.el8_4	0:5.0.204-1.el8_4

History

History
Recorded	Changed	Sources
Nov 3, 2026	affected
Nov 2, 2026	first indexed	CVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2021-31957 is a medium vulnerability (CVSS 5.9) in Microsoft .net, published June 8, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 5.14%, the 92nd percentile. Fixed in dotnet 5.0.7.

References

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