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CVE-2021-26423

26
FAUCET Score

CVE-2021-26423 is a Denial of Service vulnerability affecting Microsoft .NET Core and Visual Studio products. With a CVSS score of 7.5 (High), it allows unauthenticated remote attackers to cause a denial of service with low attack complexity. While the vulnerability has a low EPSS score and is not listed in CISA's KEV catalog, there is no public exploit code available (Metasploit, Nuclei, ExploitDB), and it has received minimal community discussion and media coverage, suggesting limited active exploitation.

Impacted Technologies

VendorProductVersion(s)CPE
>= 5.0, <= 5.0.8CPE matchmatch criteria
cpe:2.3:a:microsoft:.net:*:*:*:*:*:*:*:*
>= 2.1, <= 2.1.28CPE matchmatch criteria
cpe:2.3:a:microsoft:.net_core:*:*:*:*:*:*:*:*
>= 3.1, <= 3.1.17CPE matchmatch criteria
cpe:2.3:a:microsoft:.net_core:*:*:*:*:*:*:*:*
>= 7.0, < 7.0.7CPE matchmatch criteria
cpe:2.3:a:microsoft:powershell_core:*:*:*:*:*:*:*:*
>= 7.1, < 7.1.4CPE matchmatch criteria
cpe:2.3:a:microsoft:powershell_core:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

7.5HIGH

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 Impact
NONE
Integrity Impact
NONE
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
3.6
CvssVersion
3.1

Exploit Intelligence

EPSS Score
3.86%
Probability of exploitation in next 30 days
EPSS Percentile
89.1%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0386 is in the 81st percentile among its peer group of 51,506 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.1 Mastodon, and 0.4 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (49)

microsoftpatch availablevia nvd_reference
View patch
microsoftpatch availablevia msrc
Product: PowerShell Core 7.0Fixed in: 7.0.7
View patch
microsoftpatch availablevia msrc
Product: PowerShell Core 7.1Fixed in: 7.1.4
View patch
microsoftpatch availablevia msrc
Product: .NET 5.0Fixed in: 5.0.9
View patch
microsoftpatch availablevia msrc
Product: .NET Core 3.1Fixed in: 3.1.18
View patch
microsoftpatch availablevia msrc
Product: Microsoft Visual Studio 2017 version 15.9 (includes 15.0 - 15.8)Fixed in: 15.9.38
View patch
microsoftpatch availablevia msrc
Product: Microsoft Visual Studio 2019 version 16.4 (includes 16.0 - 16.3)Fixed in: 16.4.25
View patch
microsoftpatch availablevia msrc
Product: Microsoft Visual Studio 2019 version 16.7 (includes 16.0 – 16.6)Fixed in: 16.7.18
View patch
microsoftpatch availablevia msrc
Product: Microsoft Visual Studio 2019 version 16.9 (includes 16.0 - 16.8)Fixed in: 16.9.10
View patch
microsoftpatch availablevia msrc
Product: Microsoft Visual Studio 2019 version 16.10 (includes 16.0 - 16.9)Fixed in: 16.10.5
View patch
microsoftpatch availablevia msrc
Product: Visual Studio 2019 for Mac version 8.10Fixed in: 8.10.7
View patch
microsoftpatch availablevia msrc
Product: .NET Core 2.1Fixed in: 2.1.30
View patch
nugetpatch availablevia ghsa
Product: Microsoft.NETCore.App.Runtime.Mono.LLVM.osx-x64Fixed in: 5.0.9
nugetpatch availablevia ghsa
Product: Microsoft.NETCore.App.Runtime.Mono.LLVM.linux-x64Fixed in: 5.0.9
nugetpatch availablevia ghsa
Product: Microsoft.NETCore.App.Runtime.Mono.LLVM.linux-arm64Fixed in: 5.0.9
nugetpatch availablevia ghsa
Product: Microsoft.NETCore.App.Runtime.Mono.LLVM.AOT.osx-x64Fixed in: 5.0.9
nugetpatch availablevia ghsa
Product: Microsoft.NETCore.App.Runtime.Mono.LLVM.AOT.linux-x64Fixed in: 5.0.9
nugetpatch availablevia ghsa
Product: Microsoft.NETCore.App.Runtime.Mono.LLVM.AOT.linux-arm64Fixed in: 5.0.9
nugetpatch availablevia ghsa
Product: Microsoft.NETCore.App.Runtime.Mono.linux-x64Fixed in: 5.0.9
nugetpatch availablevia ghsa
Product: Microsoft.NETCore.App.Runtime.Mono.linux-musl-x64Fixed in: 5.0.9
nugetpatch availablevia ghsa
Product: Microsoft.NETCore.App.Runtime.Mono.linux-arm64Fixed in: 5.0.9
nugetpatch availablevia ghsa
Product: Microsoft.NETCore.App.Runtime.Mono.linux-armFixed in: 5.0.9
nugetpatch availablevia ghsa
Product: Microsoft.NETCore.App.Runtime.linux-x64Fixed in: 3.1.18
nugetpatch availablevia ghsa
Product: Microsoft.NETCore.App.Runtime.linux-x64Fixed in: 5.0.9
nugetpatch availablevia ghsa
Product: Microsoft.NETCore.App.Runtime.linux-musl-x64Fixed in: 3.1.18
nugetpatch availablevia ghsa
Product: Microsoft.NETCore.App.Runtime.linux-musl-x64Fixed in: 5.0.9
nugetpatch availablevia ghsa
Product: Microsoft.NETCore.App.Runtime.linux-musl-arm64Fixed in: 3.1.18
nugetpatch availablevia ghsa
Product: Microsoft.NETCore.App.Runtime.linux-musl-arm64Fixed in: 5.0.9
nugetpatch availablevia ghsa
Product: Microsoft.NETCore.App.Runtime.linux-musl-armFixed in: 5.0.9
nugetpatch availablevia ghsa
Product: Microsoft.NETCore.App.Runtime.rhel.6-x64Fixed in: 3.1.18
nugetpatch availablevia ghsa
Product: Microsoft.NETCore.App.Runtime.linux-arm64Fixed in: 5.0.9
nugetpatch availablevia ghsa
Product: Microsoft.NETCore.App.Runtime.linux-armFixed in: 3.1.18
nugetpatch availablevia ghsa
Product: Microsoft.NETCore.App.Runtime.linux-armFixed in: 5.0.9
nugetpatch availablevia ghsa
Product: Microsoft.NETCore.App.Runtime.linux-arm64Fixed in: 3.1.18
nugetpatch availablevia ghsa
Product: Microsoft.NETCore.App.Runtime.win-x86Fixed in: 3.1.18
nugetpatch availablevia ghsa
Product: Microsoft.NETCore.App.Runtime.win-x86Fixed in: 5.0.9
nugetpatch availablevia ghsa
Product: Microsoft.NETCore.App.Runtime.win-x64Fixed in: 3.1.18
nugetpatch availablevia ghsa
Product: Microsoft.NETCore.App.Runtime.win-x64Fixed in: 5.0.9
nugetpatch availablevia ghsa
Product: Microsoft.NETCore.App.Runtime.win-arm64Fixed in: 3.1.18
nugetpatch availablevia ghsa
Product: Microsoft.NETCore.App.Runtime.win-arm64Fixed in: 5.0.9
nugetpatch availablevia ghsa
Product: Microsoft.NETCore.App.Runtime.win-armFixed in: 3.1.18
nugetpatch availablevia ghsa
Product: Microsoft.NETCore.App.Runtime.win-armFixed in: 5.0.9
nugetpatch availablevia ghsa
Product: Microsoft.NETCore.App.Runtime.osx-x64Fixed in: 3.1.18
nugetpatch availablevia ghsa
Product: Microsoft.NETCore.App.Runtime.osx-x64Fixed in: 5.0.9
nugetpatch availablevia ghsa
Product: Microsoft.NETCore.App.Runtime.Mono.osx-x64Fixed in: 5.0.9
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8Fixed in: dotnet5.0-0:5.0.206-1.el8_4
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8Fixed in: dotnet3.1-0:3.1.118-1.el8_4
View patch
redhatpatch availablevia redhat_api
Product: .NET Core on Red Hat Enterprise LinuxFixed in: rh-dotnet50-dotnet-0:5.0.206-1.el7_9
View patch
redhatpatch availablevia redhat_api
Product: .NET Core on Red Hat Enterprise LinuxFixed in: rh-dotnet31-dotnet-0:3.1.118-1.el7_9
View patch

Vendor Advisories (3)

nugetGHSA-rh58-r7jh-xhx3high

.NET Core Elevation of Privilege Vulnerability

Oct 25, 2022
redhatCVE-2021-26423Important

dotnet: ASP.NET Core WebSocket frame processing DoS

Aug 10, 2021
microsoft2021-Aug/CVE-2021-26423Important

.NET Core and Visual Studio Denial of Service Vulnerability

Aug 10, 2021

References

portal.msrc.microsoft.com / en-US/security-guidance/advisory/CVE-2021-26423
PatchVendor Advisory