CVE-2026-56170Network attack vector

Service interruption via unbounded stateful reconnect

Published Jul 14, 2026 · Updated Jul 14, 2026

Denial of service in ASP.NET Core SignalR in Microsoft .NET 8 through 10 allows remote attackers to interrupt service via stateful reconnect. SignalR accepts stateful reconnect activity without limiting the resources it allocates, allowing one client to exhaust capacity needed by others. Only ASP.NET Core applications with SignalR stateful reconnect enabled are exposed, and the reported consequence is loss of availability to other users.

CVSS severity7.5
High
EPSS probability1.01%
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 ASP.NET Core SignalR in Microsoft .NET 8 through 10 allows remote attackers to interrupt service via stateful reconnect. SignalR accepts stateful reconnect activity without limiting the resources it allocates, allowing one client to exhaust capacity needed by others. Only ASP.NET Core applications with SignalR stateful reconnect enabled are exposed, and the reported consequence is loss of availability to other users.

The record

CVE
CVE-2026-56170
Published
Jul 14, 2026
Updated
Jul 14, 2026
Vendor
Microsoft
Product
.NET 9.0
Classifications
CWE-770, T1499.002
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 14, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 14, 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=9.0.0 <9.0.18

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Microsoft · .NET 9.0version=9.0.0 <9.0.18
Microsoft · .NET 10.0version=10.0.0 <10.0.6
Microsoft · .NET 8version=8.0.0 <8.0.29

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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-770Allocation of Resources Without Limits or Throttling
T1499.002Service Exhaustion Flood

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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