CVE-2021-26867: 
vulnerability analysis and mitigation

Windows Hyper-V Remote Code Execution Vulnerability (CVE-2021-26867) was disclosed and patched by Microsoft in March 2021. The vulnerability affects Microsoft's Windows Hyper-V hardware virtualization product, specifically impacting Windows 10 (versions 1909, 2004, 20h2) and Windows Server 2016 systems (NVD).

The vulnerability received a CVSS v3.1 base score of 8.8 (HIGH) from NIST with vector string CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H, while Microsoft assessed it with a CVSS score of 9.9 (CRITICAL) with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H. The vulnerability is particularly relevant to systems using the Plan-9 file system within Hyper-V (Zero Day Initiative).

If successfully exploited, this vulnerability could allow an authenticated attacker to execute arbitrary code on the underlying Hyper-V server, potentially compromising the security of the host system and other virtual machines running on it (Threatpost).

The vulnerability has a low attack complexity, making exploitation more likely. However, Microsoft has indicated that exploitation requires an authenticated user with specific privileges on the system (NVD).

Microsoft released security updates to address this vulnerability as part of their March 2021 Patch Tuesday updates. The fixes are available through patches KB5000802 and KB5000808 for affected systems (Rapid7).