Summary

Microsoft Security Advisory CVE-2026-56170 – .NET Denial of Service Vulnerability

Severity

high

CVSS

7.5

EPSS

1.2% (p67)

CWE

CWE-770

Also known as

GHSA-j8gr-8fp3-5q5h#Microsoft.AspNetCore.App.Runtime.linux-arm

Published

2026-07-21

Updated

2026-07-21

Advisory details

Microsoft Security Advisory CVE-2026-56170 – .NET Denial of Service Vulnerability

Executive summary

Microsoft is releasing this security advisory to provide information about a vulnerability in ASP.NET Core SignalR (Microsoft.AspNetCore.App.Runtime). This advisory also provides guidance on what developers can do to update their applications to remove this vulnerability.

A denial of service vulnerability exists in ASP.NET Core SignalR in .NET 8, .NET 9, and .NET 10. Stateful reconnect can be leveraged by an attacker to deny service to other users.

Announcement

Announcement for this issue can be found at https://github.com/dotnet/announcements/issues/**TBD**

CVSS Details

• Version: 3.1
• Severity: High
• Score: 7.5
• Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:U/RL:O/RC:C
• Weakness: CWE-770 (Allocation of Resources Without Limits or Throttling)

Affected Platforms

• Platforms: All
• Architectures: All

Mitigation Factors

Your ASP.NET Core app is only affected if it uses SignalR with stateful reconnect enabled.

Affected Packages

The vulnerability affects any Microsoft .NET project if it uses any of affected package versions listed below

.NET 10.0

.NET 9.0

.NET 8.0

Advisory FAQ

How do I know if I am affected?

If using a package listed in affected packages, you're exposed to the vulnerability.

How do I fix the issue?

1. To fix the issue please install the la

References

• https://github.com/advisories/GHSA-j8gr-8fp3-5q5h
• https://github.com/dotnet/aspnetcore/security/advisories/GHSA-j8gr-8fp3-5q5h
• https://nvd.nist.gov/vuln/detail/CVE-2026-56170
• https://github.com/dotnet/announcements/issues/424
• https://github.com/dotnet/aspnetcore/discussions/67787
• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-56170

Related advisories

• CVE-2026-96236 — high · NuGet/Microsoft.AspNetCore.App.Runtime.linux-arm
• CVE-2026-70181 — high · NuGet/Microsoft.AspNetCore.App.Runtime.linux-arm
• CVE-2026-88092 — critical · NuGet/Microsoft.AspNetCore.App.Runtime.linux-arm
• CVE-2026-70188 — critical · NuGet/Microsoft.AspNetCore.App.Runtime.linux-arm
• CVE-2026-70186 — high · NuGet/Microsoft.AspNetCore.App.Runtime.linux-arm
• CVE-2026-70183 — high · NuGet/Microsoft.AspNetCore.App.Runtime.linux-arm
• CVE-2026-70175 — high · NuGet/Microsoft.AspNetCore.App.Runtime.linux-arm
• CVE-2026-70196 — medium · NuGet/Microsoft.AspNetCore.App.Runtime.linux-arm

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