CVE-2026-102870

The Blazor WebAssembly debug proxy embeds attacker-controlled ToString(), description, and class-name values into generated C# without consistently escaping them. When a developer evaluates an expression while debugging, the value can escape the generated string literal and execute code on the developer's machine.

A code injection vulnerability was found in the Blazor WebAssembly debug proxy of ASP.NET Core, which is shipped in the dotnet10.0 packages in Red Hat Enterprise Linux 8, 9, and 10, Red Hat In-Vehicle OS, and Fedora. The debug proxy embeds attacker-controlled values, such as ToString() results, descriptions, and class names, into generated C# code without consistently escaping them. When a developer evaluates an expression while debugging a Blazor WebAssembly application, a malicious value can escape the generated string literal and execute arbitrary code on the developer's machine. Red Hat rated this flaw as IMPORTANT (CVSS 3.1 score of 8.8, CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H), matching the upstream Microsoft severity; exploitation requires no privileges but relies on a developer interacting with attacker-controlled values during a debugging session. The .NET 8 based dotnet8.0 builds in Red Hat Hardened Images were determined to be not affected because the vulnerable component is not present there. This flaw is tracked as DELEGATED, and a fix for the affected Red Hat products is being pursued.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.