GHSA-55jh-fwmh-39m4
HIGHGHSA-55jh-fwmh-39m4 is a high-severity (CVSS 7) CWE-59 vulnerability in Microsoft.NET.Build.Containers. O3 Security confirms whether GHSA-55jh-fwmh-39m4 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Microsoft Security Advisory CVE-2026-50526 – .NET Tampering Vulnerability
Real-World Exposure
Microsoft.NET.Build.Containers.NETMicrosoft.NET.Build.Containers.NETMicrosoft.NET.Build.ContainersReal-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 .NET SDK (Microsoft.NET.Build.Containers). This advisory also provides guidance on what developers can do to update their applications to remove this vulnerability.
A tampering vulnerability exists in the .NET SDK (.NET 8, .NET 9, and .NET 10) container image build process which could allow a local attacker to inject resources that could be incorporated into container images built by other users on the same machine.
Announcement
Announcement for this issue can be found at https://github.com/dotnet/announcements/issues/**TBD**
CVSS Details
- Version: 3.1
- Severity: High
- Score: 7.0
- Vector:
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H - Weakness: CWE-59 (Improper Link Resolution Before File Access ('Link Following'))
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 10.0"></a>.NET 10.0
| Package name | Affected version | Patched version |
|---|---|---|
| Microsoft.NET.Build.Containers | >= 10.0.0, <= 10.0.9 | 10.0.10 |
<a name=".NET 9.0"></a>.NET 9.0
| Package name | Affected version | Patched version |
|---|---|---|
| Microsoft.NET.Build.Containers | >= 9.0.0, <= 9.0.17 | 9.0.18 |
<a name=".NET 8.0"></a>.NET 8.0
| Package name | Affected version | Patched version |
|---|---|---|
| Microsoft.NET.Build.Containers | >= 8.0.0, <= 8.0.28 | 8.0.29 |
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. 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 nuget package, update the package reference to the patched version. You can list the versions you have installed by running the
dotnet --infocommand.
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/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
Acknowledgements
Anonymous, Siwei Li with Microsoft
Revisions
V1.0 (July 14, 2026): Advisory published.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| .NETNuGet | Microsoft.NET.Build.Containers | ≥ 10.0.0&&< 10.0.10 | 10.0.10 |
| .NETNuGet | Microsoft.NET.Build.Containers | ≥ 9.0.0&&< 9.0.18 | 9.0.18 |
| .NETNuGet | Microsoft.NET.Build.Containers | ≥ 8.0.0&&< 8.0.29 | 8.0.29 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for Microsoft.NET.Build.Containers. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update Microsoft.NET.Build.Containers to 10.0.10 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-55jh-fwmh-39m4 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-55jh-fwmh-39m4 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-55jh-fwmh-39m4. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-55jh-fwmh-39m4 in your dependencies?
O3 detects GHSA-55jh-fwmh-39m4 across NuGet dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.