CVE-2026-83671 in Windows
Summary
by MITRE • 10/14/2026
Out-of-bounds read in Windows Hyper-V allows an authorized attacker to disclose information locally.
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Analysis
by VulDB Data Team • 10/14/2026
The vulnerability described involves an out-of-bounds read condition within the Microsoft Hyper-V hypervisor component of the Windows operating system. This specific flaw arises when the virtualization layer fails to properly validate memory access boundaries during certain operations, allowing a process running inside a guest virtual machine or potentially on the host itself if privileges are escalated to interact with hyper-v components to read data from adjacent memory regions that it should not have access to. In technical terms, this is classified under Common Weakness Enumeration as CWE-125 Out-of-bounds Read, which represents a situation where software reads past the end of an allocated buffer or array without proper bounds checking. The root cause typically stems from insufficient validation of input parameters passed between the guest operating system and the hypervisor via synthetic devices such as the Synthetic Network Adapter or Synthetic Storage Controller, which facilitate communication through hypercalls and shared memory buffers.
From a security perspective, this vulnerability is particularly concerning because it enables information disclosure to an authorized attacker who has local access to the affected system. While the attacker must already possess valid credentials on the guest OS, the ability to trigger an out-of-bounds read allows them to extract sensitive data from the host machine or other isolated virtual machines that reside in adjacent memory spaces. This can lead to the leakage of cryptographic keys, session tokens, kernel structures, or other confidential information stored within the hypervisor's address space. The operational impact is significant as it undermines the fundamental isolation guarantees provided by virtualization technologies. Attackers leveraging this flaw could potentially gain insights into host system configurations or compromise the security context of other tenants in a multi-tenant environment, thereby facilitating further lateral movement or privilege escalation attacks if combined with additional vulnerabilities.
In terms of threat modeling and attack patterns, this vulnerability aligns with ATT&CK technique T1082 System Information Discovery, where adversaries gather information about the host operating system to plan subsequent actions. Additionally, it relates to T1537 Decompress Data in Memory, as attackers may need to process or interpret raw memory dumps obtained through the out-of-bounds read to extract meaningful intelligence. The exploitation vector is primarily local, requiring physical or logical access to a user account on the guest OS with sufficient privileges to interact with hyper-v services. This distinguishes it from remote code execution vulnerabilities but places it in a high-risk category for internal threats and insider attacks where an authenticated user seeks to break out of their virtualized environment.
Mitigation strategies primarily involve applying the latest security updates provided by Microsoft, which address these memory safety issues through improved bounds checking logic within the hyper-v components. Organizations should ensure that all Windows hosts running Hyper-V are patched regularly according to vendor release schedules. Furthermore, implementing strict access controls and least privilege principles for accounts with administrative rights on guest VMs can reduce the attack surface. Network segmentation between virtual machines is also recommended to limit the potential blast radius if an attacker successfully exploits this vulnerability. Monitoring tools should be configured to detect unusual memory access patterns or hypercall frequencies that might indicate exploitation attempts, although such detection remains challenging due to the low-level nature of hypervisor interactions.