# GHSA-86xp-94pg-8r6r: Microsoft Security Advisory CVE-2026-92707 - ASP.NET Core Denial of Service Vulnerability

> Unauthenticated remote attackers can cause denial of service in ASP.NET Core SignalR applications by sending deeply nested MessagePack arrays.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 13 Oct 2026

## What is GHSA-86xp-94pg-8r6r?

GHSA-86xp-94pg-8r6r is a denial of service vulnerability in Microsoft.AspNetCore.SignalR.Protocols.MessagePack, published on 13 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

## Executive summary

Microsoft is releasing this security advisory to provide information about a vulnerability in Microsoft.AspNetCore.SignalR.Protocols.MessagePack; MessagePack; MessagePack.Annotations; MessagePackAnalyzer. This advisory also provides guidance on what developers can do to update their applications to remove this vulnerability.

SignalR's MessagePack protocol can consume excessive memory while deserializing deeply nested attacker-controlled arrays, resulting in unauthenticated remote denial of service.

## Announcement

Announcement for this issue can be found at https://github.com/dotnet/announcements/issues/473

## CVSS Details

- **Version:** 3.1
- **Severity:** Moderate
- **Score:** 5.3
- **Vector:** `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L`
- **Weakness:** CWE-1325 (Improperly Controlled Sequential Memory Allocation)

## Affected Platforms

- **Platforms:** Windows, Linux, macOS
- **Architectures:** All

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

The vulnerability affects Microsoft .NET projects that use an affected package version listed below.

Package name | Affected version | Patched version
------------ | ---------------- | ---------------
[Microsoft.AspNetCore.SignalR.Protocols.MessagePack](https://www.nuget.org/packages/Microsoft.AspNetCore.SignalR.Protocols.MessagePack) | >= 10.0.0, <= 10.0.12 | 10.0.13
[Microsoft.AspNetCore.SignalR.Protocols.MessagePack](https://www.nuget.org/packages/Microsoft.AspNetCore.SignalR.Protocols.MessagePack) | >= 11.0.0-preview.5, <= 11.0.0-rc.1 | 11.0.0-rc.2
[Microsoft.AspNetCore.SignalR.Protocols.MessagePack](https://www.nuget.org/packages/Microsoft.AspNetCore.SignalR.Protocols.MessagePack) | >= 8.0.0, <= 8.0.31 | 8.0.32
[Microsoft.AspNetCore.SignalR.Protocols.MessagePack](https://www.nuget.org/packages/Microsoft.AspNetCore.SignalR.Protocols.MessagePack) | >= 9.0.0, <= 9.0.20 | 9.0.21

## Advisory FAQ

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

If using a package listed in [affected packages](#affected-packages), you're exposed to the vulnerability.

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

1. To fix the issue please install the latest version of .NET. 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.
2. 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.

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](https://docs.microsoft.com/dotnet/core/deploying/#self-contained-deployments-scd) 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](https://msrc.microsoft.com/report/vulnerability/new). Further information can be found in the MSRC [Report an Issue FAQ](https://www.microsoft.com/msrc/faqs-report-an-issue).

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/runtime. 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.

### External Links

[CVE-2026-92707](https://www.cve.org/CVERecord?id=CVE-2026-92707)

### Acknowledgements

Anonymous

### Revisions

V1.0 (10/13/2026): Advisory published.

## Which versions are affected by GHSA-86xp-94pg-8r6r?

8 open source packages ship an affected version, including Microsoft.AspNetCore.SignalR.Protocols.MessagePack.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `Microsoft.AspNetCore.SignalR.Protocols.MessagePack` | NuGet | From 10.0.0 | 10.0.13 |
| `Microsoft.AspNetCore.SignalR.Protocols.MessagePack` | NuGet | From 10.0.0 | 10.0.13 |
| `Microsoft.AspNetCore.SignalR.Protocols.MessagePack` | NuGet | From 11.0.0-preview.5 | 11.0.0-rc.2 |
| `Microsoft.AspNetCore.SignalR.Protocols.MessagePack` | NuGet | From 11.0.0-preview.5 | 11.0.0-rc.2 |
| `Microsoft.AspNetCore.SignalR.Protocols.MessagePack` | NuGet | From 8.0.0 | 8.0.32 |
| `Microsoft.AspNetCore.SignalR.Protocols.MessagePack` | NuGet | From 8.0.0 | 8.0.32 |
| `Microsoft.AspNetCore.SignalR.Protocols.MessagePack` | NuGet | From 9.0.0 | 9.0.21 |
| `Microsoft.AspNetCore.SignalR.Protocols.MessagePack` | NuGet | From 9.0.0 | 9.0.21 |

## How do I fix GHSA-86xp-94pg-8r6r?

Upgrade Microsoft.AspNetCore.SignalR.Protocols.MessagePack to a fixed version for your release line: 10.0.13, 11.0.0-rc.2, 8.0.32 or 9.0.21.

## Is GHSA-86xp-94pg-8r6r being exploited?

There is no known exploitation of GHSA-86xp-94pg-8r6r in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for GHSA-86xp-94pg-8r6r and fix it if it is affected.

What it is: GHSA-86xp-94pg-8r6r is a denial of service vulnerability in Microsoft.AspNetCore.SignalR.Protocols.MessagePack, published on 13 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of GHSA-86xp-94pg-8r6r in the wild and no public exploit code.

Affected packages and fixed versions:
- Microsoft.AspNetCore.SignalR.Protocols.MessagePack (NuGet): affected from 10.0.0; fixed in 10.0.13
- Microsoft.AspNetCore.SignalR.Protocols.MessagePack (NuGet): affected from 10.0.0; fixed in 10.0.13
- Microsoft.AspNetCore.SignalR.Protocols.MessagePack (NuGet): affected from 11.0.0-preview.5; fixed in 11.0.0-rc.2
- Microsoft.AspNetCore.SignalR.Protocols.MessagePack (NuGet): affected from 11.0.0-preview.5; fixed in 11.0.0-rc.2
- Microsoft.AspNetCore.SignalR.Protocols.MessagePack (NuGet): affected from 8.0.0; fixed in 8.0.32
- Microsoft.AspNetCore.SignalR.Protocols.MessagePack (NuGet): affected from 8.0.0; fixed in 8.0.32
- Microsoft.AspNetCore.SignalR.Protocols.MessagePack (NuGet): affected from 9.0.0; fixed in 9.0.21
- Microsoft.AspNetCore.SignalR.Protocols.MessagePack (NuGet): affected from 9.0.0; fixed in 9.0.21

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/GHSA-86xp-94pg-8r6r/ (Markdown: https://insights.sbomify.com/GHSA-86xp-94pg-8r6r/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/GHSA-86xp-94pg-8r6r

---
From sbomify Insights: https://insights.sbomify.com/GHSA-86xp-94pg-8r6r/
Summaries are generated and may contain mistakes; the official description above is the record.