CVE-2026-81355 – Virtual Hard Disk (VHD) Miniport Driver Remote Code Execution Vulnerability

CVE-2026-81355 is a Critical remote code execution vulnerability caused by a heap-based buffer overflow in the Microsoft Virtual Hard Disk (VHD) Miniport Driver. An authorized attacker can exploit the vulnerability locally to execute code. Exploitation requires high privileges, high attack complexity, and no user interaction. The vulnerability is not publicly disclosed or known to be exploited.

CVSS SCORE: 7.5.

SEVERITY: Critical.

THREAT: An attacker with high privileges and detailed knowledge of the target system could trigger the heap-based buffer overflow and execute code locally. Successful exploitation can have a high impact on confidentiality, integrity, and availability, with the security scope extending beyond the vulnerable component.

EXPLOITS: This vulnerability is not publicly disclosed and is not reported as exploited. Exploit code maturity is classified as Unproven, and the exploitability assessment is Exploitation Less Likely. The existence of public exploit code, a zero-day exploit, or proof-of-concept code cannot be confirmed.

TECHNICAL SUMMARY: CVE-2026-81355 is a heap-based buffer overflow (CWE-122) affecting the Virtual Hard Disk (VHD) Miniport Driver. An authorized local attacker can exploit improper handling of memory to cause a heap buffer overflow and execute code. Exploitation has high complexity and requires high privileges, but no user interaction is needed. Successful exploitation is not guaranteed and depends on factors including the environment, system configuration, and additional security measures. A successful attack can result in high confidentiality, integrity, and availability impact.

EXPLOITABILITY: Affected products include Windows 10 versions 1607, 1809, 21H2, and 22H2; Windows 11 versions 23H2, 24H2, 25H2, and 26H1; and Windows Server 2012, 2012 R2, 2016, 2019, 2022, and 2025, including the listed Server Core installations. Exploitation is local, requires high privileges and high attack complexity, and requires no user interaction.

BUSINESS IMPACT: Successful code execution could compromise sensitive information, alter data or system behavior, and disrupt affected Windows endpoints or servers. Because confidentiality, integrity, and availability impacts are all rated High, exploitation on business-critical systems could create significant operational and security consequences.

WORKAROUND: No mitigations or workarounds are identified. An official fix is identified, and the applicable security update should be deployed where possible.

URGENCY: This vulnerability is rated Critical and can result in code execution with high confidentiality, integrity, and availability impact. Although exploitation is considered less likely and no active exploitation is reported, organizations should prioritize the official security update across affected Windows systems because no workaround or mitigation is identified.