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Fencer Vulns
high 7.5

CVE-2021-1723 json

ASP.NET Core and Visual Studio Denial of Service Vulnerability

published 2021-01-12 5 y ago modified 2026-06-17 4 mo ago also BIT-aspnet-core-2021-1723 , EUVD-2022-1900 , GHSA-242j-2gm6-5rwx

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
5.3%
EPSS 5.3% chance of exploitation in 30 days, percentile 92%
public exploits
0
none known

Summary

ASP.NET Core and Visual Studio Denial of Service Vulnerability

Patch / fix

  • nuget Microsoft.AspNetCore.Server.Kestrel.Core 2.1.25
  • nuget Microsoft.AspNetCore.App.Runtime.linux-arm 3.1.11, 5.0.2
  • nuget Microsoft.AspNetCore.App.Runtime.linux-arm64 3.1.11, 5.0.2
  • nuget Microsoft.AspNetCore.App.Runtime.linux-musl-arm64 3.1.11, 5.0.2
  • nuget Microsoft.AspNetCore.App.Runtime.linux-musl-x64 3.1.11, 5.0.2
  • nuget Microsoft.AspNetCore.App.Runtime.linux-x64 3.1.11, 5.0.2
  • nuget Microsoft.AspNetCore.App.Runtime.osx-x64 3.1.11, 5.0.2
  • nuget Microsoft.AspNetCore.App.Runtime.win-arm 3.1.11, 5.0.2
  • nuget Microsoft.AspNetCore.App.Runtime.win-arm64 3.1.11, 5.0.2
  • nuget Microsoft.AspNetCore.App.Runtime.win-x64 3.1.11, 5.0.2
  • nuget Microsoft.AspNetCore.App.Runtime.win-x86 3.1.11, 5.0.2
  • nuget Microsoft.AspNetCore.App.Runtime.linux-musl-arm 5.0.2
  • bitnami aspnet-core 3.1.11, 5.0.2
  • rh-dotnet31-dotnet RHEL 3.1 DOTNET 3.1.111-1.el7_9
  • rh-dotnet31-dotnet-host RHEL 3.1 DOTNET 3.1.11-1.el7_9
  • rh-dotnet31-dotnet-sdk-3.1 RHEL 3.1 DOTNET 3.1.111-1.el7_9
  • rh-dotnet31-dotnet-hostfxr-3.1 RHEL 3.1 DOTNET 3.1.11-1.el7_9
  • rh-dotnet31-dotnet-runtime-3.1 RHEL 3.1 DOTNET 3.1.11-1.el7_9
  • rh-dotnet31-dotnet-templates-3.1 RHEL 3.1 DOTNET 3.1.111-1.el7_9
  • rh-dotnet31-aspnetcore-runtime-3.1 RHEL 3.1 DOTNET 3.1.11-1.el7_9
  • rh-dotnet31-dotnet-apphost-pack-3.1 RHEL 3.1 DOTNET 3.1.11-1.el7_9

red hat advisories RHSA-2021:0114RHSA-2021:0094RHSA-2021:0096RHSA-2021:0095

  • dotnet-sdk Arch Linux 5.0.3.sdk103-2
  • dotnet-runtime Arch Linux 5.0.3.sdk103-2

arch linux advisories AVG-1449

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2021-1723 updated cvss 7.5

dotnet: ASP.NET Core Callbacks outside of locks cause Krestel deadlock when using HTTP2

  • Red Hat .NET Core on Red Hat Enterprise Linux ComputeNode (v. 7) rh-dotnet31-dotnet 3.1.111-1.el7_9, rh-dotnet50-dotnet 5.0.102-1.el7_9, rh-dotnet50-dotnet-host 5.0.2-1.el7_9, rh-dotnet31-dotnet-host 3.1.11-1.el7_9, rh-dotnet31-dotnet-sdk-3.1 3.1.111-1.el7_9, rh-dotnet50-dotnet-sdk-5.0 5.0.102-1.el7_9, +16 more Red Hat .NET Core on Red Hat Enterprise Linux Server (v. 7) rh-dotnet31-dotnet 3.1.111-1.el7_9, rh-dotnet50-dotnet 5.0.102-1.el7_9, rh-dotnet50-dotnet-host 5.0.2-1.el7_9, rh-dotnet31-dotnet-host 3.1.11-1.el7_9, rh-dotnet31-dotnet-sdk-3.1 3.1.111-1.el7_9, rh-dotnet50-dotnet-sdk-5.0 5.0.102-1.el7_9, +16 more Red Hat .NET Core on Red Hat Enterprise Linux Workstation (v. 7) rh-dotnet31-dotnet 3.1.111-1.el7_9, rh-dotnet50-dotnet 5.0.102-1.el7_9, rh-dotnet50-dotnet-host 5.0.2-1.el7_9, rh-dotnet31-dotnet-host 3.1.11-1.el7_9, rh-dotnet31-dotnet-sdk-3.1 3.1.111-1.el7_9, rh-dotnet50-dotnet-sdk-5.0 5.0.102-1.el7_9, +16 more
    fixed: vendor fix RHSA-2021:0114
  • Red Hat Enterprise Linux AppStream (v. 8) dotnet 5.0.102-2.el8_3, dotnet-host 5.0.2-2.el8_3, dotnet3.1 3.1.111-1.el8_3, dotnet5.0 5.0.102-2.el8_3, dotnet-sdk-3.1 3.1.111-1.el8_3, dotnet-sdk-5.0 5.0.102-2.el8_3, +15 more
    fixed: vendor fix RHSA-2021:0095
  • Red Hat .NET Core 2.1 on Red Hat Enterprise Linux rh-dotnet21, rh-dotnet21-runtime Red Hat Enterprise Linux 8 dotnet, dotnet-host, dotnet-sdk-2.1, dotnet-runtime-2.1, dotnet-sdk-2.1.5xx, dotnet-host-fxr-2.1 Red Hat Enterprise Linux 9 dotnet3.1
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
17 mo ago

Exploit prediction

5.30% chance of exploitation in the next 30 days, higher than 92% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 7.5 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
GitHub 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD 2.0 5.0 AV:N/AC:L/Au:N/C:N/I:N/A:P
OSV 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected packages

ecosystem package affected fixed in
nuget Microsoft.AspNetCore.Server.Kestrel.Core
<2.1.25
2.1.25
nuget Microsoft.AspNetCore.App.Runtime.linux-arm
>=3.1.0, <3.1.11
>=5.0.0, <5.0.2
3.1.11
5.0.2
nuget Microsoft.AspNetCore.App.Runtime.linux-arm64
>=3.1.0, <3.1.11
>=5.0.0, <5.0.2
3.1.11
5.0.2
nuget Microsoft.AspNetCore.App.Runtime.linux-musl-arm64
>=3.1.0, <3.1.11
>=5.0.0, <5.0.2
3.1.11
5.0.2
nuget Microsoft.AspNetCore.App.Runtime.linux-musl-x64
>=3.1.0, <3.1.11
>=5.0.0, <5.0.2
3.1.11
5.0.2
nuget Microsoft.AspNetCore.App.Runtime.linux-x64
>=3.1.0, <3.1.11
>=5.0.0, <5.0.2
3.1.11
5.0.2
nuget Microsoft.AspNetCore.App.Runtime.osx-x64
>=3.1.0, <3.1.11
>=5.0.0, <5.0.2
3.1.11
5.0.2
nuget Microsoft.AspNetCore.App.Runtime.win-arm
>=3.1.0, <3.1.11
>=5.0.0, <5.0.2
3.1.11
5.0.2
nuget Microsoft.AspNetCore.App.Runtime.win-arm64
>=3.1.0, <3.1.11
>=5.0.0, <5.0.2
3.1.11
5.0.2
nuget Microsoft.AspNetCore.App.Runtime.win-x64
>=3.1.0, <3.1.11
>=5.0.0, <5.0.2
3.1.11
5.0.2
nuget Microsoft.AspNetCore.App.Runtime.win-x86
>=3.1.0, <3.1.11
>=5.0.0, <5.0.2
3.1.11
5.0.2
nuget Microsoft.AspNetCore.App.Runtime.linux-musl-arm
>=5.0.1, <5.0.2
5.0.2
bitnami aspnet-core
>=3.1.0, <3.1.11
>=5.0.0, <5.0.2
3.1.11
5.0.2

Affected products

  • Microsoft ASP.NET Core 3.1
  • Microsoft ASP.NET Core 5.0
  • Microsoft Microsoft Visual Studio 2019 version 16.4 (includes 16.0 - 16.3)
  • Microsoft Microsoft Visual Studio 2019 version 16.8
  • Microsoft Microsoft Visual Studio 2019 version 16.7 (includes 16.0 – 16.6)

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.