CVE-2021-27063: 
vulnerability analysis and mitigation

Windows DNS Server Denial of Service Vulnerability (CVE-2021-27063) was disclosed in March 2021. The vulnerability affects Microsoft Windows DNS Server implementations and was part of Microsoft's March 2021 Patch Tuesday security updates. This vulnerability is unique from CVE-2021-26896 and affects various versions of Windows Server (NVD).

The vulnerability received a CVSS v3.1 Base Score of 7.5 (HIGH) with the vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H, indicating it is network-accessible, requires low attack complexity, and needs no privileges or user interaction to exploit. Under CVSS v2.0, it received a Base Score of 5.0 (MEDIUM) (NVD).

The vulnerability specifically affects DNS servers with dynamic updates enabled and could result in a denial of service condition, potentially disrupting DNS server operations. The impact is limited to availability, with no direct effect on confidentiality or integrity of the system (Talos Intelligence).

The vulnerability requires network access to exploit and affects DNS servers with dynamic updates enabled. While the attack complexity is considered low, there have been no reported instances of this vulnerability being exploited in the wild (Talos Intelligence).

Microsoft has released security patches to address this vulnerability. As a workaround before applying patches, administrators can enable Secure Zone Updates to limit potential attack sources, though this does not completely prevent exploitation. The recommended solution is to install Microsoft's security patch for complete protection (Talos Intelligence).