CVE-2026-103555 in Windows
Summary
by MITRE • 10/13/2026
Heap-based buffer overflow in Virtual Hard Disk (VHD) Miniport Driver allows an authorized attacker to elevate privileges locally.
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Analysis
by VulDB Data Team • 10/13/2026
The vulnerability identified involves a heap-based buffer overflow within the Microsoft Virtual Hard Disk miniport driver, specifically affecting components responsible for managing virtual disk operations on Windows systems. This type of flaw typically arises when the software fails to properly validate the size or bounds of user-supplied data before copying it into a pre-allocated memory region on the heap. In this specific context, an attacker who has already gained local access and possesses valid authentication credentials can trigger malformed requests that exceed the allocated buffer limits. The overflow allows for writing data beyond the intended boundaries of the heap allocation, which can corrupt adjacent memory structures or overwrite critical control data such as function pointers or exception handling records.
From a technical perspective, this vulnerability is classified under CWE-122, Heap-based Buffer Overflow, and aligns with MITRE ATT&CK technique T1068, Exploitation for Privilege Escalation. The core issue lies in the lack of rigorous boundary checks during the processing of VHD-related IOCTL requests or internal driver routines that handle disk image metadata. When an authorized user interacts with the virtual hard disk subsystem using specially crafted inputs, they can manipulate the heap layout to achieve arbitrary code execution within the context of the operating system kernel or a high-privilege process. This is particularly dangerous because miniport drivers operate at a low level in the Windows Driver Model stack, often running with SYSTEM-level privileges, thereby providing a direct path from user-mode application space to kernel mode.
The operational impact of this vulnerability is severe due to its potential for local privilege escalation. An attacker who exploits this flaw can execute arbitrary code with elevated permissions, effectively taking full control of the affected system. This compromises the confidentiality, integrity, and availability of all data stored on or accessible through that machine. Furthermore, because the exploit requires prior authentication, it represents a significant risk in environments where insider threats are prevalent or where attackers have already breached perimeter defenses to reach local user accounts. The ability to escalate privileges from a standard user account to SYSTEM level bypasses many security controls designed to limit damage from compromised low-privilege processes.
Mitigation strategies primarily involve applying the latest security updates and patches provided by Microsoft, which address the input validation deficiencies in the VHD miniport driver. Organizations should ensure that all Windows systems are configured for automatic update delivery or monitored closely for patch availability regarding this specific vulnerability. Additionally, implementing strict access control policies to limit local login capabilities can reduce the attack surface. Security teams should also monitor for anomalous behavior indicative of heap exploitation attempts and consider deploying endpoint detection and response solutions capable of identifying memory corruption anomalies in kernel-mode drivers. Regular auditing of user privileges and enforcing the principle of least privilege further diminishes the likelihood that an attacker will have the necessary local access to attempt this exploit.