How severe is CVE-2019-0564?

CVE-2019-0564 has a CVSS score of 7.5/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2019-0564?

CVE-2019-0564 affects the following packages: Microsoft.AspNetCore.WebSockets (NuGet), Microsoft.AspNetCore.WebSockets (NuGet), Microsoft.AspNetCore.Server.Kestrel.Core (NuGet), System.Net.WebSockets.WebSocketProtocol (NuGet), Microsoft.NETCore.App (NuGet), Microsoft.NETCore.App (NuGet), Microsoft.AspNetCore.App (NuGet), Microsoft.AspNetCore.App (NuGet), and 2 more. Ecosystems affected: NuGet.

How do I fix CVE-2019-0564?

Update Microsoft.AspNetCore.WebSockets to 2.2.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2019-0564 is resolved across your whole dependency graph.

How do I detect CVE-2019-0564 in my NuGet dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for Microsoft.AspNetCore.WebSockets, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2019-0564 if there is no patch (or I can't update yet)?

Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Is CVE-2019-0564 actively exploited in the wild?

No public exploit code has been indexed for CVE-2019-0564 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2019-0564?

CVE-2019-0564 has an EPSS (Exploit Prediction Scoring System) score of 8.4%, placing it in the 95th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2019-0564?

CVE-2019-0564 is classified as CWE-19 (CWE-19). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2019-0564 published, and has it been updated?

CVE-2019-0564 was published on January 8, 2019 and was last updated on October 24, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

.NET

.NET NuGet

Not in CISA KEV

HIGH severity

CVE-2019-0564 — Microsoft.AspNetCore.WebS…

HIGH

CVE-2019-0564 is a high-severity (CVSS 7.5) CWE-19 vulnerability in Microsoft.AspNetCore.WebSockets. A fix is available for Microsoft.AspNetCore.WebSockets — see the affected versions and patch details below.

Denial of service in ASP.NET Core

Also known asGHSA-6px8-22w5-w334

Published

Jan 8, 2019

Updated

Oct 24, 2026

Affected

10 pkgs

Patched

10 / 10

Exploits

None indexed

Exploitation data as of Nov 6, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

8.4%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs95th percentile — riskier than 95% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

10 pkgs affected

.NETMicrosoft.AspNetCore.WebSockets.NETMicrosoft.AspNetCore.WebSockets.NETMicrosoft.AspNetCore.Server.Kestrel.Core.NETSystem.Net.WebSockets.WebSocketProtocol.NETMicrosoft.NETCore.App.NETMicrosoft.NETCore.App.NETMicrosoft.AspNetCore.App.NETMicrosoft.AspNetCore.App+2 more

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects NuGet packages — download data is not available via public APIs for these ecosystems.

Description

A denial of service vulnerability exists when ASP.NET Core improperly handles web requests, aka "ASP.NET Core Denial of Service Vulnerability." This affects ASP.NET Core 2.1. This CVE ID is unique from CVE-2019-0548.

Affected Packages

10 total 10 fixed

Ecosystem	Package	Vulnerable range	Fix
.NETNuGet	`Microsoft.AspNetCore.WebSockets`	≥ 2.2.0&&< 2.2.1	2.2.1`dotnet add package Microsoft.AspNetCore.WebSockets --version 2.2.1`
.NETNuGet	`Microsoft.AspNetCore.WebSockets`	≥ 2.1.0&&< 2.1.7	2.1.7`dotnet add package Microsoft.AspNetCore.WebSockets --version 2.1.7`
.NETNuGet	`Microsoft.AspNetCore.Server.Kestrel.Core`	≥ 2.1.0&&< 2.1.7	2.1.7`dotnet add package Microsoft.AspNetCore.Server.Kestrel.Core --version 2.1.7`
.NETNuGet	`System.Net.WebSockets.WebSocketProtocol`	≥ 4.5.0&&< 4.5.3	4.5.3`dotnet add package System.Net.WebSockets.WebSocketProtocol --version 4.5.3`
.NETNuGet	`Microsoft.NETCore.App`	≥ 2.2.0&&< 2.2.1	2.2.1`dotnet add package Microsoft.NETCore.App --version 2.2.1`
.NETNuGet	`Microsoft.NETCore.App`	≥ 2.1.0&&< 2.1.7	2.1.7`dotnet add package Microsoft.NETCore.App --version 2.1.7`

Affected Products

1 product · 1 configurations

Application

asp.net coremicrosoft

1 version

2.1

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for Microsoft.AspNetCore.WebSockets, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update Microsoft.AspNetCore.WebSockets to 2.2.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2019-0564 is resolved across your whole dependency graph.
Workarounds
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatModerate

Product	Fixed in	Advisory
.NET Core on Red Hat Enterprise Linux	`rh-dotnet21-0:2.1-6.el7`	RHSA-2019:0040

Frequently Asked Questions

O3 Security · Impact-Aware SCA

Is CVE-2019-0564 in your dependencies?

Find it across NuGet, including transitive dependencies.

Scan my dependencies How O3 SCA works

CVSS Score

7.5/10CVSS v3 base

Vector breakdown

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

Raw vector

CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CWE Classification

CWE-19CWE-19

Weaponization

No Nuclei template, Metasploit module or public proof-of-concept found.

OpenSSF Scorecard

Package health score

Announcements

4.4/10

Code-Review3/10

Maintained1/10

Branch-Protection6/10

Assessed Nov 2, 2026

Timeline

Disclosed

Jan 8, 2019

Last updated

Oct 24, 2026

Identifiers

CVE-2019-0564

GHSA-6px8-22w5-w334

References

Advisorysecurityfocus.com Advisoryaccess.redhat.com · RHSA 2019:0040 Advisorynvd.nist.gov · CVE 2019 0564 Fixportal.msrc.microsoft.com · CVE 2019 0564 Webgithub.com Webgithub.com

Related vulnerabilities

This CVE is high severity; 3 of 5 other CVEs affecting Microsoft.AspNetCore.Server.Kestrel.Core are rated as high or higher (top: critical).

CVE-2025-55315CVE-2021-1723CVE-2018-0787GHSA-3m2r-q8x3-xmf7GHSA-cgpw-2gph-2r9g

Provenance

Sources

OSV.devNVDFIRST.org (EPSS)

Last verifiedOct 24, 2026

CVE-2019-0564 — Microsoft.AspNetCore.WebS…

EPSS Exploitation Probability

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

Description

Affected Packages

Affected Products

Detection & mitigation playbook

Detect

Fix

Workarounds

Fixing This On Your OS

Frequently Asked Questions

Is CVE-2019-0564 in your dependencies?