Executive brief
A security vulnerability has been identified in Microsoft .NET, a widely used framework for building and running applications. The flaw exists in how the system handles secure encrypted connections (TLS/SSL), potentially allowing an attacker to bypass security checks that verify if a user or system is authorized to perform certain actions. This could lead to unauthorized access to sensitive data or functions within affected applications.
Technical details
This vulnerability is classified as an Incorrect Authorization (CWE-863) issue within the System.Net.Security namespace of .NET. The root cause lies in the SslStream implementation, which fails to properly enforce authorization checks during the processing of TLS/SSL connections. An unauthenticated remote attacker can exploit this flaw over the network without user interaction to bypass security features. The vulnerability affects .NET 8, 9, and 10 across all supported platforms and architectures. Microsoft has released patches in versions 8.0.29, 9.0.18, and 10.0.10. Developers using self-contained deployments must recompile and redeploy their applications to incorporate the fix.
Affected products
- Microsoft .NET Core App Runtime 8.0.0 - 8.0.28, 9.0.0 - 9.0.17, 10.0.0 - 10.0.9
Timeline
- 2026-07-14: advisory: Initial advisory publication
- 2026-07-20: patched: Updated advisory with patched version details
References
- https://github.com/dotnet/runtime/security/advisories/GHSA-qvw7-jm5c-6hqw
- https://github.com/dotnet/announcements/issues/417
- https://github.com/dotnet/runtime/issues/130713
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-50528
- https://api.github.com/repos/dotnet/runtime/security-advisories/GHSA-qvw7-jm5c-6hqw