GHSA-8fh9-c4jq-94h4 idunno.Bluesky, idunno.AtProto and idunno.AtProto.OAuthCallback Denial of Service Vulnerability

Not scored Published

A denial of service vulnerability in a transitive dependency affects Bluesky and AtProto libraries, requiring an upgrade to resolve.

Exploited in the wild
Not known
Login needed
Not stated
Attackable
Over the internet
Victim action needed
Not stated
Fix
Available

What is GHSA-8fh9-c4jq-94h4?

GHSA-8fh9-c4jq-94h4 is a denial of service vulnerability in idunno.AtProto, published on 13 Mar 2026. It can be exploited over the network.

Official description

idunno.Bluesky, idunno.AtProto and idunno.AtProto.OAuthCallback Denial of Service Vulnerability

Impact

The Microsoft.Bcl.Memory package, a transitive dependency of idunno.AtProto and idunno.AtProto.OAuthCallback had a Denial of Service security vulnerability, CVE-2026-26127

Patches

v1.7.0 updates the dependencies on Duende.IdentityModel.OidcClient and Duende.IdentityModel.OidcClient.Extensions which, in turn, updates their dependency on Microsoft.Bcl.Memory to 10.0.4, resolving the vulnerability.

Workarounds

No workarounds exist for this vulnerability.

How to fix the issue

To update your dependencies on idunno.Bluesky, idunno.AtProto and idunno.AtProto.OAuthCallback,

Using the .NET CLI (Command Line Interface):

  • Open a terminal or command prompt in your project's directory.

  • To update a specific package to its latest version, use the following add package command:

    • If you are using idunno.Bluesky dotnet package update idunno.Bluesky

    • If you are using idunno.AtProto as a direct dependency dotnet package update idunno.AtProto

    • If you are using idunno.AtProto.OAuthCallback as a direct dependency dotnet package update idunno.AtProto.OAuthCallback

Using the NuGet Package Manager Console in Visual Studio:

  • Open your project in Visual Studio.

  • Navigate to "Tools > NuGet Package Manager > Package Manager Console".

  • To update a specific package to its latest version, use the following Update-Package command:

    • If you are using idunno.Bluesky Update-Package -Id idunno.Bluesky

    • If you are using idunno.AtProto as a direct dependency Update-Package -Id idunno.AtProto

    • If you are using idunno.AtProto.OAuthCallback as a direct dependency Update-Package -Id idunno.AtProto.OAuthCallback

NuGet Package Manager UI in Visual Studio:

  • Open your project in Visual Studio.
  • Right-click on your project in Solution Explorer and select "Manage NuGet Packages…" or navigate to "Project > Manage NuGet Packages".
  • In the NuGet Package Manager window, select the "Updates" tab. This tab lists packages with available updates from your configured package sources.
  • Select the package(s) you wish to update. You can choose a specific version from the dropdown or update to the latest available version.
  • Click the "Update" button.

References

Which versions are affected by GHSA-8fh9-c4jq-94h4?

6 open source packages ship an affected version, including idunno.AtProto, idunno.AtProto.OAuthCallback and idunno.Bluesky.

PackageAffectedFixed in
idunno.AtProto NuGetAll versions1.7.0
idunno.AtProto NuGetAll versions1.7.0
idunno.AtProto.OAuthCallback NuGetAll versions1.7.0
idunno.AtProto.OAuthCallback NuGetAll versions1.7.0
idunno.Bluesky NuGetAll versions1.7.0
idunno.Bluesky NuGetAll versions1.7.0

How do I fix GHSA-8fh9-c4jq-94h4?

Upgrade idunno.AtProto to 1.7.0 or later.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is GHSA-8fh9-c4jq-94h4 being exploited?

There is no known exploitation of GHSA-8fh9-c4jq-94h4 in the wild and no public exploit code.

Sources

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