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This vulnerability is caused by an integer underflow (CWE-191) within the Windows Hyper-V virtualization stack. An integer underflow, or wraparound, occurs when an arithmetic operation decreases a value below the minimum limit of its defined data type. In a signed integer, this can flip the value to a very large positive number. Within Hyper-V’s kernel-mode components (like storage Virtualization Service Providers), such integers often track buffer lengths, offsets, or loop counters. A network-authenticated attacker can send a specially crafted request to trigger this flaw. The underflow corrupts these calculations, potentially causing the driver to allocate incorrect amounts of memory, perform out-of-bounds read/write operations, or bypass safety checks. This leads to a kernel fault or resource exhaustion in the host, resulting in a denial-of-service (DoS) condition that can crash the Hyper-V host and disrupt all hosted virtual machines.
Platform: Windows Hyper-V
Version: 10/11/Server
Vulnerability: Integer Underflow DoS
Severity: Medium
date: 2025-12-09
Prediction: 2025-12-09
What Undercode Say:
Analytics
– `Get-WindowsUpdateLog`
– `driverquery /v | findstr storvsp`
– `Get-CimInstance Win32_OperatingSystem | Select BuildNumber`
How Exploit:
Method
An authorized attacker with low-privileged network access sends a maliciously crafted network request to a target Hyper-V host. This payload triggers the integer underflow in a vulnerable kernel driver. The flawed calculation causes a kernel-level fault, crashing the host system and denying service to all virtual machines.
Status
No public proof-of-concept exploit is available. There is no evidence of active in-the-wild exploitation.
Protection from this CVE
Immediate Action
Apply Microsoft’s December 2025 security updates immediately via Windows Update or the Microsoft Update Catalog. The patch corrects the integer arithmetic in the affected Hyper-V component.
Compensating Controls
If patching is delayed, restrict network access to Hyper-V management interfaces. Segment Hyper-V management and live migration traffic onto separate, secured networks. Enforce least-privilege access for Hyper-V administration.
Impact
Primary Consequence
A successful attack causes a denial-of-service condition on the Hyper-V host. This leads to system instability and the temporary unavailability of all virtualized workloads running on that host, potentially affecting many dependent services.
Scope and Limitations
The vulnerability is rated Medium (CVSS:3.1 5.3) with impacts only to Availability (A:H). It does not allow for confidentiality breach (C:N) or integrity compromise (I:N). Exploitation requires an authenticated attacker (PR:L) and has high attack complexity (AC:H).
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Sources:
Reported By: nvd.nist.gov
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