How severe is GHSA-f8h2-vmm9-qhj6?

GHSA-f8h2-vmm9-qhj6 has a CVSS score of 7.5/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by GHSA-f8h2-vmm9-qhj6?

GHSA-f8h2-vmm9-qhj6 affects the following packages: Microsoft.AspNetCore.App.Runtime.linux-x64 (NuGet), Microsoft.AspNetCore.App.Runtime.linux-x64 (NuGet), Microsoft.AspNetCore.App.Runtime.linux-x64 (NuGet), Microsoft.AspNetCore.App.Runtime.win-x64 (NuGet), Microsoft.AspNetCore.App.Runtime.win-x64 (NuGet), Microsoft.AspNetCore.App.Runtime.win-x64 (NuGet), Microsoft.AspNetCore.App.Runtime.osx-arm64 (NuGet), Microsoft.AspNetCore.App.Runtime.osx-arm64 (NuGet), and 4 more. Ecosystems affected: NuGet.

How do I fix GHSA-f8h2-vmm9-qhj6?

Update Microsoft.AspNetCore.App.Runtime.linux-x64 to 8.0.28 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-f8h2-vmm9-qhj6 is resolved across your whole dependency graph.

How do I detect GHSA-f8h2-vmm9-qhj6 in my NuGet dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for Microsoft.AspNetCore.App.Runtime.linux-x64, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate GHSA-f8h2-vmm9-qhj6 if there is no patch (or I can't update yet)?

Stop feeding it untrusted input: reject or quarantine files and payloads from unverified sources until you can upgrade, restrict accepted formats to the ones you actually need, and run the parsing or decoding step in a least-privileged sandbox or short-lived worker so a crash or corrupted read cannot reach the rest of the process.

Is GHSA-f8h2-vmm9-qhj6 actively exploited in the wild?

No public exploit code has been indexed for GHSA-f8h2-vmm9-qhj6 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 GHSA-f8h2-vmm9-qhj6?

GHSA-f8h2-vmm9-qhj6 has an EPSS (Exploit Prediction Scoring System) score of 2.4%, placing it in the 84th 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 GHSA-f8h2-vmm9-qhj6?

GHSA-f8h2-vmm9-qhj6 is classified as Uncontrolled Resource Consumption (CWE-400), CWE-770 (CWE-770). These weakness types describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was GHSA-f8h2-vmm9-qhj6 published, and has it been updated?

GHSA-f8h2-vmm9-qhj6 was published on June 15, 2026 and was last updated on September 10, 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

GHSA-f8h2-vmm9-qhj6 — Microsoft.AspNetCore.App.…

HIGH

GHSA-f8h2-vmm9-qhj6 is a high-severity (CVSS 7.5) Uncontrolled Resource Consumption vulnerability in Microsoft.AspNetCore.App.Runtime.linux-x64. A fix is available for Microsoft.AspNetCore.App.Runtime.linux-x64 — see the affected versions and patch details below.

Microsoft Security Advisory CVE-2026-45591 – ASP.NET Core Denial of Service Vulnerability

Also known asBIT-aspnet-core-2026-45591BIT-dotnet-2026-45591BIT-dotnet-sdk-2026-45591CVE-2026-45591

Published

Jun 15, 2026

Updated

Sep 10, 2026

Affected

12 pkgs

Patched

12 / 12

Exploits

None indexed

Exploitation data as of Sep 27, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for GHSA-f8h2-vmm9-qhj6.

EPSS Exploitation Probability

via FIRST.org ↗

2.4%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs84th percentile — riskier than 84% of all scored CVEsHighest risk

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

How urgent is this, really

GHSA-f8h2-vmm9-qhj6 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 379,842 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

12 pkgs affected

.NETMicrosoft.AspNetCore.App.Runtime.linux-x64.NETMicrosoft.AspNetCore.App.Runtime.linux-x64.NETMicrosoft.AspNetCore.App.Runtime.linux-x64.NETMicrosoft.AspNetCore.App.Runtime.win-x64.NETMicrosoft.AspNetCore.App.Runtime.win-x64.NETMicrosoft.AspNetCore.App.Runtime.win-x64.NETMicrosoft.AspNetCore.App.Runtime.osx-arm64.NETMicrosoft.AspNetCore.App.Runtime.osx-arm64+4 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

Executive summary

Microsoft is releasing this security advisory to provide information about a vulnerability in ASP.NET Core SignalR and Blazor Server. 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 the MessagePack hub protocol used by SignalR and Blazor Server where an attacker can send deeply-nested MessagePack arrays to cause a stack overflow, resulting in a denial of service.

Announcement

Announcement for this issue can be found at https://github.com/dotnet/announcements/issues/405

Affected Platforms

Platforms: All
Architectures: All

<a name="affected-packages"></a>Affected Packages

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

<a name=".NET 10"></a>.NET 10

Package name	Affected version	Patched version
Microsoft.AspNetCore.App.Runtime.linux-arm	>= 10.0.0, <= 10.0.8	10.0.9
Microsoft.AspNetCore.App.Runtime.linux-arm64	>= 10.0.0, <= 10.0.8	10.0.9
Microsoft.AspNetCore.App.Runtime.linux-musl-arm	>= 10.0.0, <= 10.0.8	10.0.9
Microsoft.AspNetCore.App.Runtime.linux-musl-arm64	>= 10.0.0, <= 10.0.8	10.0.9
Microsoft.AspNetCore.App.Runtime.linux-musl-x64	>= 10.0.0, <= 10.0.8	10.0.9
Microsoft.AspNetCore.App.Runtime.linux-x64	>= 10.0.0, <= 10.0.8	10.0.9
Microsoft.AspNetCore.App.Runtime.osx-arm64	>= 10.0.0, <= 10.0.8	10.0.9
Microsoft.AspNetCore.App.Runtime.osx-x64	>= 10.0.0, <= 10.0.8	10.0.9
Microsoft.AspNetCore.App.Runtime.win-arm	>= 10.0.0, <= 10.0.8	10.0.9
Microsoft.AspNetCore.App.Runtime.win-arm64	>= 10.0.0, <= 10.0.8	10.0.9
Microsoft.AspNetCore.App.Runtime.win-x64	>= 10.0.0, <= 10.0.8	10.0.9
Microsoft.AspNetCore.App.Runtime.win-x86	>= 10.0.0, <= 10.0.8	10.0.9

<a name=".NET 10 SignalR"></a>Microsoft.AspNetCore.SignalR.Protocols.MessagePack (.NET 10)

Package name	Affected version	Patched version
Microsoft.AspNetCore.SignalR.Protocols.MessagePack	>= 10.0.0, <= 10.0.8	10.0.9

<a name=".NET 9"></a>.NET 9

Package name	Affected version	Patched version
Microsoft.AspNetCore.App.Runtime.linux-arm	>= 9.0.0, <= 9.0.16	9.0.17
Microsoft.AspNetCore.App.Runtime.linux-arm64	>= 9.0.0, <= 9.0.16	9.0.17
Microsoft.AspNetCore.App.Runtime.linux-musl-arm	>= 9.0.0, <= 9.0.16	9.0.17
Microsoft.AspNetCore.App.Runtime.linux-musl-arm64	>= 9.0.0, <= 9.0.16	9.0.17
Microsoft.AspNetCore.App.Runtime.linux-musl-x64	>= 9.0.0, <= 9.0.16	9.0.17
Microsoft.AspNetCore.App.Runtime.linux-x64	>= 9.0.0, <= 9.0.16	9.0.17
Microsoft.AspNetCore.App.Runtime.osx-arm64	>= 9.0.0, <= 9.0.16	9.0.17
Microsoft.AspNetCore.App.Runtime.osx-x64	>= 9.0.0, <= 9.0.16	9.0.17
Microsoft.AspNetCore.App.Runtime.win-arm	>= 9.0.0, <= 9.0.16	9.0.17
Microsoft.AspNetCore.App.Runtime.win-arm64	>= 9.0.0, <= 9.0.16	9.0.17
Microsoft.AspNetCore.App.Runtime.win-x64	>= 9.0.0, <= 9.0.16	9.0.17
Microsoft.AspNetCore.App.Runtime.win-x86	>= 9.0.0, <= 9.0.16	9.0.17

<a name=".NET 9 SignalR"></a>Microsoft.AspNetCore.SignalR.Protocols.MessagePack (.NET 9)

Package name	Affected version	Patched version
Microsoft.AspNetCore.SignalR.Protocols.MessagePack	>= 9.0.0, <= 9.0.16	9.0.17

<a name=".NET 8"></a>.NET 8

Package name	Affected version	Patched version
Microsoft.AspNetCore.App.Runtime.linux-arm	>= 8.0.0, <= 8.0.27	8.0.28
Microsoft.AspNetCore.App.Runtime.linux-arm64	>= 8.0.0, <= 8.0.27	8.0.28
Microsoft.AspNetCore.App.Runtime.linux-musl-arm	>= 8.0.0, <= 8.0.27	8.0.28
Microsoft.AspNetCore.App.Runtime.linux-musl-arm64	>= 8.0.0, <= 8.0.27	8.0.28
Microsoft.AspNetCore.App.Runtime.linux-musl-x64	>= 8.0.0, <= 8.0.27	8.0.28
Microsoft.AspNetCore.App.Runtime.linux-x64	>= 8.0.0, <= 8.0.27	8.0.28
Microsoft.AspNetCore.App.Runtime.osx-arm64	>= 8.0.0, <= 8.0.27	8.0.28
Microsoft.AspNetCore.App.Runtime.osx-x64	>= 8.0.0, <= 8.0.27	8.0.28
Microsoft.AspNetCore.App.Runtime.win-arm	>= 8.0.0, <= 8.0.27	8.0.28
Microsoft.AspNetCore.App.Runtime.win-arm64	>= 8.0.0, <= 8.0.27	8.0.28
Microsoft.AspNetCore.App.Runtime.win-x64	>= 8.0.0, <= 8.0.27	8.0.28
Microsoft.AspNetCore.App.Runtime.win-x86	>= 8.0.0, <= 8.0.27	8.0.28

<a name=".NET 8 SignalR"></a>Microsoft.AspNetCore.SignalR.Protocols.MessagePack (.NET 8)

Package name	Affected version	Patched version
Microsoft.AspNetCore.SignalR.Protocols.MessagePack	>= 8.0.0, <= 8.0.27	8.0.28

Advisory FAQ

<a name="how-affected"></a>How do I know if I am affected?

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

<a name="how-fix"></a>How do I fix the issue?

To fix the issue please install the latest version of .NET 10.0, .NET 9.0, or .NET 8.0. If you have installed one or more .NET SDKs through Visual Studio, Visual Studio will prompt you to update Visual Studio, which will also update your .NET SDKs.
If your application references the vulnerable package, update the package reference to the patched version. You can list the versions you have installed by running the dotnet --info command.

If you're using .NET 8.0, you should download and install .NET 8.0.28 Runtime or .NET 8.0.xxx SDK from https://dotnet.microsoft.com/download/dotnet-core/8.0.
If you're using .NET 9.0, you should download and install .NET 9.0.17 Runtime or .NET 9.0.xxx SDK from https://dotnet.microsoft.com/download/dotnet-core/9.0.
If you're using .NET 10.0, you should download and install .NET 10.0.9 Runtime or .NET 10.0.xxx SDK from https://dotnet.microsoft.com/download/dotnet-core/10.0.

Once you have installed the updated runtime or SDK, restart your apps for the update to take effect.

Additionally, if you've deployed self-contained applications targeting any of the impacted versions, these applications are also vulnerable and must be recompiled and redeployed.

Other Information

Reporting Security Issues

If you have found a potential security issue in a supported version of .NET, please report it to the Microsoft Security Response Center (MSRC) via the MSRC Researcher Portal. Further information can be found in the MSRC Report an Issue FAQ.

Security reports made through MSRC may qualify for the Microsoft .NET Bounty. Details of the Microsoft .NET Bounty Program including terms and conditions are at https://aka.ms/corebounty.

Support

You can ask questions about this issue on GitHub in the .NET GitHub organization. The main repos are located at https://github.com/dotnet/aspnetcore. The Announcements repo (https://github.com/dotnet/Announcements) will contain this bulletin as an issue and will include a link to a discussion issue. You can ask questions in the linked discussion issue.

Disclaimer

The information provided in this advisory is provided "as is" without warranty of any kind. Microsoft disclaims all warranties, either express or implied, including the warranties of merchantability and fitness for a particular purpose. In no event shall Microsoft Corporation or its suppliers be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages, even if Microsoft Corporation or its suppliers have been advised of the possibility of such damages. Some states do not allow the exclusion or limitation of liability for consequential or incidental damages so the foregoing limitation may not apply.

Acknowledgements

Anonymous

Affected Packages

12 total 12 fixed

Ecosystem	Package	Vulnerable range	Fix
.NETNuGet	`Microsoft.AspNetCore.App.Runtime.linux-x64`	≥ 8.0.0&&< 8.0.28	8.0.28`dotnet add package Microsoft.AspNetCore.App.Runtime.linux-x64 --version 8.0.28`
.NETNuGet	`Microsoft.AspNetCore.App.Runtime.linux-x64`	≥ 9.0.0&&< 9.0.17	9.0.17`dotnet add package Microsoft.AspNetCore.App.Runtime.linux-x64 --version 9.0.17`
.NETNuGet	`Microsoft.AspNetCore.App.Runtime.linux-x64`	≥ 10.0.0&&< 10.0.9	10.0.9`dotnet add package Microsoft.AspNetCore.App.Runtime.linux-x64 --version 10.0.9`
.NETNuGet	`Microsoft.AspNetCore.App.Runtime.win-x64`	≥ 8.0.0&&< 8.0.28	8.0.28`dotnet add package Microsoft.AspNetCore.App.Runtime.win-x64 --version 8.0.28`
.NETNuGet	`Microsoft.AspNetCore.App.Runtime.win-x64`	≥ 9.0.0&&< 9.0.17	9.0.17`dotnet add package Microsoft.AspNetCore.App.Runtime.win-x64 --version 9.0.17`
.NETNuGet	`Microsoft.AspNetCore.App.Runtime.win-x64`	≥ 10.0.0&&< 10.0.9	10.0.9`dotnet add package Microsoft.AspNetCore.App.Runtime.win-x64 --version 10.0.9`

Affected Products

3 products · 7 configurations

Application

.netmicrosoft

≥ 10.0.0 && < 10.0.9

range

Application

asp.net coremicrosoft

≥ 10.0.0 && < 10.0.9

range

Application

visual studio 2026microsoft

≥ 18.6.0 && < 18.6.3

range

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.App.Runtime.linux-x64, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update Microsoft.AspNetCore.App.Runtime.linux-x64 to 8.0.28 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-f8h2-vmm9-qhj6 is resolved across your whole dependency graph.
Workarounds
Stop feeding it untrusted input: reject or quarantine files and payloads from unverified sources until you can upgrade, restrict accepted formats to the ones you actually need, and run the parsing or decoding step in a least-privileged sandbox or short-lived worker so a crash or corrupted read cannot reach the rest of the process.

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 HatImportant

This vulnerability affects the MessagePack hub protocol implementation used by ASP.NET Core SignalR and Blazor Server. Red Hat Product Security has assessed this issue as an Important severity vulnerability. The flaw occurs when processing deeply nested MessagePack arrays supplied by a remote attacker. Insufficient…

Workaround published by Red Hat

Red Hat is not aware of a practical temporary workaround that fully mitigates this issue or meets Red Hat Product Security's standards for usability, deployment, applicability, or stability. Customers are advised to apply the relevant security updates when they become available.

Source: Red Hat security advisory for GHSA-f8h2-vmm9-qhj6 (CC BY 4.0)

Product	Fixed in	Advisory
Red Hat Enterprise Linux 10	`dotnet8.0-0:8.0.128-1.el10_2`	RHSA-2026:25111
Red Hat Enterprise Linux 10	`dotnet9.0-0:9.0.118-1.el10_2`	RHSA-2026:25112
Red Hat Enterprise Linux 10	`dotnet10.0-0:10.0.109-1.el10_2`	RHSA-2026:25115
Red Hat Enterprise Linux 10.0 Extended Update Support	`dotnet8.0-0:8.0.128-1.el10_0`	RHSA-2026:28007
Red Hat Enterprise Linux 10.0 Extended Update Support	`dotnet9.0-0:9.0.118-1.el10_0`	RHSA-2026:28009
Red Hat Enterprise Linux 8	`dotnet8.0-0:8.0.128-1.el8_10`	RHSA-2026:25110
Red Hat Enterprise Linux 8	`dotnet9.0-0:9.0.118-1.el8_10`	RHSA-2026:25113
Red Hat Enterprise Linux 8	`dotnet10.0-0:10.0.109-1.el8_10`	RHSA-2026:25114

Frequently Asked Questions

## Executive summary Microsoft is releasing this security advisory to provide information about a vulnerability in ASP.NET Core SignalR and Blazor Server. 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 the MessagePack hub protocol used by SignalR and Blazor Server where an attacker can send deeply-nested MessagePack arrays to cause a stack overflow, resulting in a denial of service. ## Announcement Announcement for this issue can be found at https://github.com/dotnet/annou

O3 Security · Impact-Aware SCA

Is GHSA-f8h2-vmm9-qhj6 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:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CWE Classification

CWE-400Uncontrolled Resource Consumption CWE-770CWE-770

Weaponization

No known public exploit tooling found.

Timeline

Disclosed

Jun 15, 2026

Last updated

Sep 10, 2026

Identifiers

GHSA-f8h2-vmm9-qhj6

BIT-aspnet-core-2026-45591

BIT-dotnet-2026-45591

BIT-dotnet-sdk-2026-45591

References

Advisorynvd.nist.gov Webgithub.com Webgithub.com Webgithub.com Webmsrc.microsoft.com Packagegithub.com

Related vulnerabilities

This CVE is high severity; 8 of 8 other CVEs affecting Microsoft.AspNetCore.App.Runtime.linux-x64 are rated as high or higher (top: critical).

CVE-2026-56170CVE-2026-45591CVE-2026-42899CVE-2026-26130CVE-2025-55315CVE-2025-24070CVE-2024-38229CVE-2024-35264

Provenance

Sources

OSV.devNVDFIRST.org (EPSS)

Last verifiedSep 10, 2026

GHSA-f8h2-vmm9-qhj6 — Microsoft.AspNetCore.App.…

Exploitation Status

No confirmed exploitation observed yet

EPSS Exploitation Probability

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

Description

Executive summary

Announcement

Affected Platforms

<a name="affected-packages"></a>Affected Packages

<a name=".NET 10"></a>.NET 10

<a name=".NET 10 SignalR"></a>Microsoft.AspNetCore.SignalR.Protocols.MessagePack (.NET 10)

<a name=".NET 9"></a>.NET 9

<a name=".NET 9 SignalR"></a>Microsoft.AspNetCore.SignalR.Protocols.MessagePack (.NET 9)

<a name=".NET 8"></a>.NET 8

<a name=".NET 8 SignalR"></a>Microsoft.AspNetCore.SignalR.Protocols.MessagePack (.NET 8)

Advisory FAQ

<a name="how-affected"></a>How do I know if I am affected?

<a name="how-fix"></a>How do I fix the issue?

Other Information

Reporting Security Issues

Support

Disclaimer

Acknowledgements

Affected Packages

Affected Products

Detection & mitigation playbook

Detect

Fix

Workarounds

Fixing This On Your OS

Frequently Asked Questions

Is GHSA-f8h2-vmm9-qhj6 in your dependencies?