Microsoft has released patches for a critical vulnerability in ASP.NET Core’s Kestrel web server, rated 9.9 on the CVSS scale. The flaw, involving request smuggling, could bypass security measures depending on application code. Developers are urged to evaluate risks and apply updates promptly.
Critical Security Flaw Identified in ASP.NET Core
Microsoft has addressed a highly critical vulnerability in ASP.NET Core, specifically within its Kestrel web server component, according to reports. The flaw, designated as CVE-2025-55315, has been assigned a CVSS score of 9.9, which sources indicate is the highest ever recorded by Microsoft for such issues. Security program manager Barry Dorrans described it as a “security feature bypass,” emphasizing that the severity reflects worst-case scenarios where the vulnerability could significantly alter security scope.