CVE-2026-47300 Microsoft CVE debrief

Who should care

Users of .NET, particularly those using versions 8.0.0 to 8.0.29, 9.0.0 to 9.0.18, and 10.0.0 to 10.0.6, should be aware of this vulnerability and take necessary actions to mitigate it. .NET developers, administrators, and security teams should review the official advisory and take steps to patch or mitigate the vulnerability in their environments.

Technical summary

The vulnerability is caused by an incorrect implementation of the authentication algorithm in ASP.NET Core, allowing an authorized attacker to elevate privileges over a network. The CVSS vector is CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. This vulnerability affects .NET versions 8.0.0 to 8.0.29, 9.0.0 to 9.0.18, and 10.0.0 to 10.0.6. The incorrect authentication algorithm implementation could allow attackers to bypass security checks and gain elevated access.

Defensive priority

High priority should be given to patching affected .NET versions, particularly those with CVSS score of 8.8. Immediate action is required to prevent potential elevation of privileges by attackers.

Recommended defensive actions

• Apply patches for affected .NET versions
• Review and update .NET configurations to ensure secure authentication
• Monitor .NET applications for suspicious activity
• Consider implementing additional security measures such as network segmentation and access controls
• Review compensating controls for exposed systems while remediation is scheduled and verified

Evidence notes

The CVE record and NVD detail provide information on the vulnerability, including its CVSS score, affected versions, and CVSS vector. However, the details on affected .NET versions and configurations are limited. Defenders should verify the specific .NET versions used in their environments and review the official advisory for accurate information on affected scope and mitigation steps.

Official resources