GHSA-8FH9-C4JQ-94H4

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

• Microsoft Security Advisory CVE-2026-26127 – .NET Denial of Service Vulnerability
• CVE-2026-26127

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

GHSA-8FH9-C4JQ-94H4 has a CVSS score of 7.5 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.7.0); upgrading removes the vulnerable code path.

Kodem intelligence

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.

1. What is GHSA-8FH9-C4JQ-94H4? GHSA-8FH9-C4JQ-94H4 is a high-severity security vulnerability in idunno.AtProto (nuget), affecting versions < 1.7.0. It is fixed in 1.7.0.
2. How severe is GHSA-8FH9-C4JQ-94H4? GHSA-8FH9-C4JQ-94H4 has a CVSS score of 7.5 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which packages are affected by GHSA-8FH9-C4JQ-94H4?
   • idunno.AtProto (nuget) (versions < 1.7.0)
   • idunno.AtProto.OAuthCallback (nuget) (versions < 1.7.0)
   • idunno.Bluesky (nuget) (versions < 1.7.0)
4. Is there a fix for GHSA-8FH9-C4JQ-94H4? Yes. GHSA-8FH9-C4JQ-94H4 is fixed in 1.7.0. Upgrade to this version or later.
5. Is GHSA-8FH9-C4JQ-94H4 exploitable, and should I be worried? Whether GHSA-8FH9-C4JQ-94H4 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether GHSA-8FH9-C4JQ-94H4 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix GHSA-8FH9-C4JQ-94H4?
   • Upgrade idunno.AtProto to 1.7.0 or later
   • Upgrade idunno.AtProto.OAuthCallback to 1.7.0 or later
   • Upgrade idunno.Bluesky to 1.7.0 or later