CVE-2026-45591Network attack vector

Remote application crash via nested MessagePack arrays

Published Jun 9, 2026 · Updated Jun 9, 2026

Denial of service in ASP.NET Core 8.0, 9.0, and 10.0 allows remote attackers to crash SignalR and Blazor Server applications. The MessagePack hub protocol recursively processes attacker-supplied, deeply nested arrays until stack exhaustion triggers an unhandled stack overflow. Exposure requires an application to use SignalR or Blazor Server with the affected MessagePack protocol; the reported consequence is application termination without data disclosure or modification.

CVSS severity7.5
High
EPSS probability2.48%
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 8.0, 9.0, and 10.0 allows remote attackers to crash SignalR and Blazor Server applications. The MessagePack hub protocol recursively processes attacker-supplied, deeply nested arrays until stack exhaustion triggers an unhandled stack overflow. Exposure requires an application to use SignalR or Blazor Server with the affected MessagePack protocol; the reported consequence is application termination without data disclosure or modification.

The record

CVE
CVE-2026-45591
Published
Jun 9, 2026
Updated
Jun 9, 2026
Vendor
Microsoft
Product
ASP.NET Core 8.0
Classifications
CWE-400, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 9, 2026CVE publishedPublication date reported by the CVE source.
  2. Jun 9, 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 <8.0.28

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Microsoft · ASP.NET Core 8.0version=8.0 <8.0.28
Microsoft · ASP.NET Core 9.0version=9.0 <9.0.17
Microsoft · .NET 9.0version=9.0.0 <9.0.17
Microsoft · .NET 10.0version=10.0.0 <10.0.9
Microsoft · Microsoft Visual Studio 2026version=18.6.0 <18.6.3
Microsoft · .NET 8version=8.0.0 <8.0.28
Microsoft · ASP.NET Core 10.0version=10.0 <10.0.9

Published CVSS scores

7.5Microsoft CorporationCVSS: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
T1499.004Application or System Exploitation

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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