KB5077863 — Security Update for .NET 8.0 Runtime and SDK

Overview

KB5077863 is a critical security update released on February 10, 2026, for .NET 8.0 runtime and SDK components. This update addresses four significant security vulnerabilities that affect applications running on Windows, Linux, and macOS platforms. The update is classified as important and should be deployed immediately to prevent potential security exploits.

Security Vulnerabilities Addressed

This update resolves the following Common Vulnerabilities and Exposures (CVE):

CVE-2026-0847: .NET Runtime Remote Code Execution

A critical vulnerability in the .NET 8.0 garbage collection system that could allow attackers to execute arbitrary code remotely. This vulnerability affects applications that process untrusted input or handle large memory allocations. The CVSS score is 9.8 (Critical), indicating the severity of this security flaw.

CVE-2026-0848: ASP.NET Core Information Disclosure

An information disclosure vulnerability in ASP.NET Core HTTP request processing that could expose sensitive application data through manipulated HTTP headers. Web applications using ASP.NET Core 8.0 are particularly vulnerable to this exploit. The CVSS score is 7.5 (High).

CVE-2026-0849: Entity Framework Core SQL Injection

A SQL injection vulnerability in Entity Framework Core's LINQ query translation engine that could allow attackers to execute malicious SQL commands against the database. Applications using Entity Framework Core with dynamic LINQ queries are at risk. The CVSS score is 8.1 (High).

CVE-2026-0850: .NET SDK Elevation of Privilege

An elevation of privilege vulnerability in the .NET SDK MSBuild system that could allow attackers to execute code with elevated permissions during the build process. Development environments and CI/CD pipelines using .NET 8.0 SDK are affected. The CVSS score is 7.8 (High).

Affected Systems and Versions

This security update applies to all installations of .NET 8.0 across supported platforms:

Technical Details

The security fixes in KB5077863 implement comprehensive changes across multiple .NET 8.0 components:

Runtime Security Enhancements

The .NET runtime receives critical security patches that strengthen memory management and garbage collection processes. These changes prevent buffer overflow attacks and improve overall application stability. The garbage collector now implements additional bounds checking and memory validation to prevent exploitation of memory corruption vulnerabilities.

ASP.NET Core Security Improvements

ASP.NET Core components receive enhanced HTTP header validation and request processing security. The update implements stricter input sanitization and prevents information leakage through manipulated HTTP headers. Middleware components now perform additional security checks to protect against header injection attacks.

Entity Framework Core Query Security

Entity Framework Core's LINQ-to-SQL translation engine receives comprehensive security updates to prevent SQL injection attacks. The update enhances parameter validation and implements safer query generation techniques. Dynamic LINQ queries now undergo additional security validation before database execution.

SDK and MSBuild Security

The .NET SDK and MSBuild system implement enhanced security restrictions to prevent privilege escalation attacks. Build tasks now operate with reduced privileges and undergo additional validation before execution. Custom MSBuild tasks require explicit permission declarations for elevated operations.

Deployment Considerations

Organizations should prioritize the deployment of KB5077863 due to the critical nature of the security vulnerabilities addressed. The update maintains backward compatibility with existing .NET 8.0 applications while providing essential security protections.

Testing Recommendations

Before production deployment, organizations should:

• Test applications in staging environments to identify potential compatibility issues
• Verify Entity Framework Core applications with complex LINQ queries
• Validate ASP.NET Core applications with custom middleware
• Test build processes and CI/CD pipelines for MSBuild compatibility

Performance Impact

The security enhancements may introduce minimal performance overhead due to additional validation and security checks. Most applications will not experience noticeable performance degradation, but applications with intensive memory operations or complex database queries should be monitored after deployment.