CVE-2025-48822: Windows 10 1607 Hyper-V RCE Vulnerability

CVE-2025-48822 Overview

CVE-2025-48822 is an out-of-bounds read vulnerability in Windows Hyper-V that allows an unauthorized attacker to execute code locally. The flaw, classified as [CWE-125], affects Microsoft's Type-1 hypervisor across supported Windows client and server platforms. Successful exploitation requires user interaction and crosses a security boundary, indicated by the scope change in the CVSS vector. Microsoft published the advisory on July 8, 2025, and it remains unexploited in the wild according to CISA KEV.

Critical Impact

An attacker with local access can leverage an out-of-bounds read in Hyper-V to execute arbitrary code, potentially escaping the guest virtual machine and impacting the host with high confidentiality, integrity, and availability consequences.

Affected Products

• Microsoft Windows 10 (1607, 1809, 21H2, 22H2)
• Microsoft Windows 11 (22H2, 23H2, 24H2)
• Microsoft Windows Server 2016, 2019, 2022, 2022 23H2, and 2025

Discovery Timeline

• 2025-07-08 - CVE-2025-48822 published to NVD with Microsoft advisory release
• 2025-07-15 - Last updated in NVD database

Technical Details for CVE-2025-48822

Vulnerability Analysis

The vulnerability resides in Windows Hyper-V, Microsoft's native hardware virtualization platform. An out-of-bounds read condition occurs when the hypervisor processes attacker-controlled input without properly validating buffer boundaries. The flaw enables a local attacker to read memory beyond intended allocations and ultimately achieve code execution. Because Hyper-V mediates between guest virtual machines and the host kernel, exploitation can break the isolation boundary that virtualization is designed to enforce. The scope change in the CVSS metrics confirms that an attack against one security authority impacts another, consistent with a guest-to-host escape scenario.

Root Cause

The root cause is improper bounds checking when Hyper-V parses structured data passed through virtualization interfaces. The component reads memory outside the bounds of an allocated buffer ([CWE-125]), exposing adjacent memory contents and creating conditions that an attacker can chain into arbitrary code execution. Microsoft has not published low-level technical details of the vulnerable code path.

Attack Vector

Exploitation requires local access and user interaction. An attacker operating within a guest virtual machine, or a low-privileged local user on a Hyper-V host, can craft input that triggers the out-of-bounds read. Successful exploitation grants code execution that breaches the virtualization boundary, compromising the integrity of the host system and any co-resident workloads.

No verified proof-of-concept code is publicly available. Refer to the Microsoft CVE-2025-48822 Advisory for vendor-supplied technical details.

Detection Methods for CVE-2025-48822

Indicators of Compromise

• Unexpected vmms.exe or vmwp.exe crashes, hangs, or restarts on Hyper-V hosts that may indicate exploitation attempts against the hypervisor worker process.
• Anomalous child processes spawned by Hyper-V worker processes or unexpected loading of unsigned modules into virtualization components.
• Windows Event Log entries in Microsoft-Windows-Hyper-V-Worker and Microsoft-Windows-Hyper-V-Hypervisor channels showing abnormal guest exits or VMBus errors.

Detection Strategies

• Monitor for guest virtual machines issuing malformed hypercalls or unusual VMBus traffic patterns that deviate from baseline workload behavior.
• Correlate host-side memory access violations with guest activity timestamps to identify potential guest-to-host escape attempts.
• Apply behavioral analytics to detect privilege transitions originating from low-privileged users interacting with virtualization APIs.

Monitoring Recommendations

• Enable verbose Hyper-V logging and forward Microsoft-Windows-Hyper-V-* event channels to a centralized SIEM for retention and analysis.
• Track patch compliance across all Hyper-V hosts and prioritize systems hosting multi-tenant or untrusted guest workloads.
• Audit local user accounts on Hyper-V hosts and restrict interactive logon to administrators with documented operational need.

How to Mitigate CVE-2025-48822

Immediate Actions Required

• Apply the July 2025 Microsoft security updates referenced in the Microsoft CVE-2025-48822 Advisory to all affected Windows client and server builds.
• Prioritize patching on Hyper-V hosts running untrusted, multi-tenant, or internet-exposed guest workloads.
• Validate that automatic update rings are reaching virtualization hosts and reboot to complete hypervisor patch installation.

Patch Information

Microsoft released cumulative security updates addressing CVE-2025-48822 as part of the July 8, 2025 Patch Tuesday cycle. Updates are available through Windows Update, WSUS, and the Microsoft Update Catalog for all listed Windows 10, Windows 11, and Windows Server versions. Consult the Microsoft CVE-2025-48822 Advisory for the specific KB articles applicable to each affected build.

Workarounds

• Restrict local logon rights on Hyper-V hosts to a minimal set of trusted administrators to reduce the local attack surface.
• Limit guest virtual machine operators to users with verified operational need, and isolate untrusted workloads on dedicated hosts.
• Where Hyper-V is not required, disable the role using Disable-WindowsOptionalFeature -Online -FeatureName Microsoft-Hyper-V until patches are applied.

# Verify Hyper-V patch status on a Windows host
Get-HotFix | Sort-Object -Property InstalledOn -Descending | Select-Object -First 10

# Disable Hyper-V role if not required (requires reboot)
Disable-WindowsOptionalFeature -Online -FeatureName Microsoft-Hyper-V-All