CVE-2024-21386Network attack vector

Unauthenticated service interruption through SignalR clients

Published Feb 13, 2024 · Updated Aug 10, 2026

Denial of service in Microsoft ASP.NET Core 6.0 through 8.0 SignalR allows remote attackers to interrupt applications. Microsoft has not published the SignalR code path or the malformed client operation that consumes resources. Any unauthenticated network client that can reach a SignalR endpoint can trigger the availability-only impact; confidentiality and integrity remain unaffected.

CVSS severity7.5
High
EPSS probability2.40%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in Microsoft ASP.NET Core 6.0 through 8.0 SignalR allows remote attackers to interrupt applications. Microsoft has not published the SignalR code path or the malformed client operation that consumes resources. Any unauthenticated network client that can reach a SignalR endpoint can trigger the availability-only impact; confidentiality and integrity remain unaffected.

The record

CVE
CVE-2024-21386
Published
Feb 13, 2024
Updated
Aug 10, 2026
Vendor
Microsoft
Product
ASP.NET Core 8.0
Classifications
CWE-400, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 13, 2024CVE publishedPublication date reported by the CVE source.
  2. Aug 10, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=8.0 <8.0.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Microsoft · ASP.NET Core 8.0version=8.0 <8.0.2
Microsoft · ASP.NET Core 6.0version=6.0 <6.0.27
Microsoft · Microsoft Visual Studio 2022 version 17.8version=17.8.0 <17.8.7
Microsoft · Microsoft Visual Studio 2022 version 17.6version=17.6.0 <17.6.12
Microsoft · ASP.NET Core 7.0version=7.0.0 <7.0.16
Microsoft · Microsoft Visual Studio 2022 version 17.4version=17.4.0 <17.4.16

Published CVSS scores

7.5MicrosoftCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-400Uncontrolled Resource Consumption
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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