CVE-2025-54112: Local Privilege Escalation in VHD/VHDX Parsing

Microsoft’s Security Response Guide lists CVE-2025-54112 as a vulnerability in the Microsoft Virtual Hard Disk (VHD/VHDX) handling code that can be abused by an authorized local attacker to achieve elevation of privilege on Windows hosts, a condition vendors and incident responders classify as high priority for patching and mitigation. (msrc.microsoft.com)

Background / Overview​

Microsoft’s Virtual Hard Disk (VHD/VHDX) support is a long-standing Windows feature used by Hyper-V, Windows Sandbox, the Windows Subsystem for Linux (when using disk images), and by admins or users who mount disk images for testing and recovery. Vulnerabilities in VHD handling are a recurring attack surface because Windows treats mounted virtual disks as local block devices with privileged kernel-mode drivers, and bugs there can translate into kernel or SYSTEM-level impacts.
The vendor advisory for CVE-2025-54112 is published in Microsoft’s Security Update Guide, but the Update Guide content is rendered dynamically and requires a JavaScript-enabled view to see the full advisory details; readers and administrators should view the MSRC entry directly for the authoritative list of affected builds and KB identifiers. (msrc.microsoft.com)
Independent reporting around Microsoft’s 2025 patch cycles shows multiple Virtual Hard Disk related CVEs across the year, and security publications consistently describe VHD-related flaws as memory-safety issues (for example stack overflows, buffer over-reads, or use-after-free) that may produce local elevation of privilege outcomes when successfully exploited. These independent summaries provide context for the practical risk even when the vendor advisory is terse. (bleepingcomputer.com, news.sophos.com)

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What the bulletin says (summary of the published material)​

• Microsoft has catalogued CVE-2025-54112 in the Security Update Guide as a Virtual Hard Disk vulnerability that allows a local, authorized attacker to elevate privileges on an affected host. (msrc.microsoft.com)
• The public tracking and media coverage for related VHD issues in 2025 shows multiple Virtual Hard Disk vulnerabilities disclosed across several Patch Tuesday releases; reporter summaries consistently label these as elevation of privilege issues rooted in memory corruption in VHD/VHDX parsing code. (bleepingcomputer.com, news.sophos.com)
• At the time of publication, many community trackers and write-ups caution administrators to treat VHD-related kernel vulnerabilities as high priority because they can be chained from a local foothold into a full host compromise. (thewindowsupdate.com, threatdown.com)

Caveat — the MSRC page requires a JavaScript-enabled browser to present the interactive advisory. Where the vendor listing is not directly viewable through static scraping tools, confirm exact affected builds and KB patch identifiers in the Microsoft Update Catalog or via your organization’s patch-management console before broad rollouts. (msrc.microsoft.com)

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Technical analysis: what “use-after-free in Virtual Hard Disk” means in practice​

Memory-safety errors in disk-image parsing​

A use-after-free (UAF) occurs when software frees an object from memory but later continues to use a reference to that freed memory. In the Windows kernel or kernel-mode drivers that implement VHD/VHDX parsing and mounting, UAFs can enable:

• Corruption of in-kernel pointers or structures.
• Overwrite of function pointers or vtables, enabling control-flow redirection.
• Arbitrary read/write primitives in kernel memory (depending on the specific bug and exploitation technique).

When such memory corruption occurs in code that runs in kernel mode (as VHD drivers and Hyper-V integration components do), the attacker can often escalate privileges from a user-level or guest VM context to SYSTEM or kernel-level execution. Multiple VHD-related advisories in 2025 followed this same high-level pattern: memory-safety defect → local exploit vector → EoP impact. (bleepingcomputer.com, news.sophos.com)

Why virtual disk code is high-value to attackers​

Virtual disk handling code often accepts complex inputs (image headers, descriptors, metadata, filesystem structures embedded in images). These parsers are non-trivial and historically have harbored mistakes in bounds checking, length arithmetic, and lifecycle management of kernel objects. That complexity, combined with the privileged execution context, makes VHD parsing a recurring high-impact target. Security analysts who reviewed adjacent Hyper‑V and VHD advisories in 2025 flagged the same root causes (buffer overflows, numeric truncation, and use-after-free) as recurrent themes.

Exploitation prerequisites (high-level)​

• Local access: An attacker must be on the host (local account) or have code running inside a guest VM that can trigger the vulnerable VHD handling path. Microsoft’s language for the advisory emphasizes an authorized local attacker vector. (msrc.microsoft.com)
• Ability to provide or mount a crafted VHD/VHDX image or otherwise interact with the vulnerable APIs that parse disk images.
• Timing or heap grooming in the case of UAFs — real exploitation may require additional steps (spraying memory, shaping allocations) that increase complexity, but determined attackers and exploit developers can often overcome those hurdles in a real-world threat scenario.

Security reporting on prior VHD and Hyper‑V vulnerabilities shows these requirements do not make the flaw purely theoretical; threat actors routinely combine phishing or remote code execution to gain a local foothold and then pivot using EoP bugs to fully compromise hosts. (bleepingcomputer.com)

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Affected systems and scope — who should act first​

• Any Windows host that mounts or interacts with VHD/VHDX images.
• Hyper‑V hosts and management servers (production virtualization clusters).
• Developer and workstation systems with Hyper‑V enabled (Windows Sandbox, WSL variants that leverage virtual disks).
• Backup appliances, forensic systems, and servers that inspect or mount guest disk images.
• Cloud providers or hosting platforms that run Windows hypervisors built on Microsoft virtualization stacks.

Because the vendor advisory is precise in naming the vulnerable component but dynamic in its UI presentation, administrators must verify the exact OS versions and builds listed in the MSRC entry and the Microsoft Update Catalog before deciding which KBs to apply in each environment. (msrc.microsoft.com)

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Impact assessment and operational risk​

• Privilege escalation to SYSTEM or kernel context can enable host compromise, fabrication of persistent backdoors, credential theft, and lateral movement across enterprise networks. When Hyper‑V hosts are affected, a compromised host can threaten multiple tenant VMs and services.
• Even if full host compromise is not achieved, memory corruption in kernel-mode drivers commonly leads to system instability and denials-of-service (crashes, BSOD), which can disrupt critical services.
• The exploitability of a UAF or buffer-overflow in VHD parsing is not purely theoretical; previous CVEs in the Virtual Hard Disk code in 2025 were treated as real operational threats in enterprise advisories and prioritized by security teams. (news.sophos.com, bleepingcomputer.com)

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Verification and cross-checking (what was validated)​

• The MSRC Security Update Guide lists CVE‑2025‑54112 as a Virtual Hard Disk elevation of privilege vulnerability; the interactive page is the vendor’s canonical advisory. Administrators should retrieve the MSRC entry in a browser to see the full details and affected builds. (msrc.microsoft.com)
• Multiple independent security outlets and patch-roundup reports from 2025 document Virtual Hard Disk vulnerabilities across Microsoft patch cycles and group these as memory-safety EoP issues; these independent writeups corroborate the practical impact and patching urgency. (bleepingcomputer.com, news.sophos.com)
• Internal and community analyses included with the user’s uploads emphasize the same mitigation and response playbook for Hyper‑V and VHD-related kernel vulnerabilities: patch first, isolate management networks, inventory VHD-mounting hosts, and tune detection telemetry. These internal notes are consistent with vendor guidance and community practice.

Important verification note: some public CVE trackers and static snapshots may refer to different VHD CVEs in 2025 (the year saw numerous nearby IDs). Where the advisory or CVE description is ambiguous in third‑party summaries, cross-check the exact KB numbers and build versions against Microsoft’s Update Catalog and your patch-management tooling to ensure correct remediation mappings.

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Mitigation and prioritized action plan (practical checklist)​

• Patch immediately (highest priority)
• Identify the KB article(s) that Microsoft publishes to remediate CVE‑2025‑54112 in the Microsoft Update Catalog or through MSRC, then stage and deploy those patches through WSUS / SCCM / MEM / your endpoint manager. Confirm on a small pilot group before wide rollout. (msrc.microsoft.com)
• If patching cannot occur immediately, reduce exposure
• Prevent untrusted users from mounting VHD/VHDX images. Use Group Policy and endpoint controls to block image mounting for non-admins.
• Isolate Hyper‑V management and migration networks (dedicated VLANs / management fabric).
• Restrict who can access Hyper‑V Manager, Virtual Machine Manager consoles, and remote management APIs with strict ACLs and jump hosts.
• Apply least privilege principles
• Audit and restrict local admin rights. Avoid day-to-day accounts that have local administrator privileges.
• Disable unnecessary guest-host integration features (clipboard sharing, file copy, device redirection) for VMs that don’t require them.
• Enhance monitoring and detection
• Alert on vmms.exe or Hyper‑V service crashes, repeated mount/unmount operations, and unusual creation of snapshots or VHD mount events.
• Hunt for Mount-DiskImage, mountvol, and Mount-VHD/PowerShell usage by non-admin users in the last 72 hours.
• Post-patch validation
• Verify KB and build revisions after patching. Validate Hyper‑V operational features (live migration, checkpointing) in a controlled environment.
• Watch vendor errata: Microsoft occasionally ships follow-up microfixes if regressions occur for particular configurations.

Short-term compensations when patching is delayed:

• Block execution from removable or untrusted mounted images.
• Enforce multi‑factor authentication for administrative access to Hyper‑V hosts.
• Use EDR to detect kernel-mode exploitation primitives and unusual process behavior following mounts.

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Detection and forensic indicators​

Key signals to monitor in EDR, SIEM and host telemetry:

• Kernel crashes or system bugcheck events tied to VHD-related drivers and vmms.exe restarts.
• Unusual or repeated Mount-DiskImage or Mount-VHD PowerShell commands executed by non-privileged users.
• Sudden creation of snapshots, unexpected VM configuration changes, or new services following mount events.
• Abnormal guest-host integration channel activity (frequent service calls from a VM to the host).
• New privileged tokens or unexpected SYSTEM-level operations created following a VHD mount operation.

Investigations should preserve memory and disk images for hosts suspected of exploitation and correlate mount events with process creation and network traffic to hunt for lateral movement.

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Enterprise patching playbook (recommended sequence)​

• Identify and inventory all systems that mount or could mount VHD/VHDX images.
• Pull the authoritative MSRC advisory for CVE‑2025‑54112 and record the KB numbers for each affected OS/build. (msrc.microsoft.com)
• Stage patches on representative hosts (management servers, domain controllers, Hyper‑V clusters) and run functional test suites for live migration and backup operations.
• Roll out in phased waves with telemetry checks after each wave.
• Apply post-deployment verification queries that confirm both the KB revision and operational stability.

This sequence balances urgency with operational safety for critical virtualization infrastructure.

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Strengths, gaps, and risks — critical appraisal​

• Strengths: Microsoft’s inclusion of CVE‑2025‑54112 in the Security Update Guide is correct and gives administrators a canonical place to retrieve KBs and fix mappings. Independent reporting across reputable security outlets confirms numerous VHD-related fixes across 2025, so the overall vendor response cadence is consistent with established product security practices. (msrc.microsoft.com, news.sophos.com)
• Gaps / friction points: The MSRC Update Guide’s dynamic UI can complicate automated scraping or quick offline verification, and public third‑party trackers sometimes lag or summarize the vendor text inconsistently. Administrators must therefore confirm the exact KB and build list using the Update Catalog or their patch-management tooling rather than relying solely on third-party summaries. (msrc.microsoft.com)
• Risk profile: Virtual Hard Disk code sits in privileged execution paths; a successful exploit can be elevated to SYSTEM or kernel privileges. Although the attack vector is local/authorized, real-world attacks commonly chain a non‑privileged foothold (phishing, RCE) with a local EoP to achieve full compromise. Treat this CVE with high priority in patching and detection programs. (bleepingcomputer.com)

Unverifiable claim flag — where precise exploitation details (e.g., whether the bug is a classic use-after-free, stack overflow, arithmetic truncation, or buffer over-read) are inconsistent across third‑party summaries, treat the exact root-cause classification as provisional until you view the full MSRC advisory and the Microsoft KB. Third‑party sites grouped multiple Virtual Hard Disk CVEs during 2025, and some of those nearby CVE IDs describe different memory-safety defects; therefore avoid mixing technical details from adjacent CVEs without confirming the specific CVE mapping. (msrc.microsoft.com, bleepingcomputer.com)

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Practical recommendations for Windows enthusiasts and admins​

• Prioritize patching hosts that run Hyper‑V, host management services, or mount external disk images.
• Reduce the number of users who can mount VHD/VHDX images, and remove local admin rights from day-to-day accounts.
• Harden and isolate the management plane for virtualization infrastructure.
• Tune detection rules in EDR and SIEM to correlate mounts and unexpected service crashes.
• Maintain a validated rollback plan and test patches in non-production environments where possible.

For smaller environments or single-host users, the same principles apply: install the vendor patch as soon as it is published for your Windows build, and avoid mounting untrusted disk images until patches are deployed. (threatdown.com)

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Conclusion​

CVE‑2025‑54112 joins a string of Virtual Hard Disk and Hyper‑V related vulnerabilities that made 2025 particularly busy for Windows kernel and virtualization security. The vendor advisory is authoritative and should be used to identify affected builds and KB numbers, but administrators must take a pragmatic, layered approach: patch quickly, restrict who can mount images, isolate management networks, and tune detection telemetry for mounts and kernel-level anomalies. Independent reporting and the community guidance that accompanied Microsoft’s 2025 patch cycles all point to the same operational reality — memory-safety issues in VHD parsing are not purely theoretical, and they deserve immediate, prioritized remediation. (msrc.microsoft.com, bleepingcomputer.com, news.sophos.com)
For administrators planning action now: retrieve the MSRC advisory for CVE‑2025‑54112 in a browser, record the KB and affected builds, stage the update for Hyper‑V hosts first, and implement the compensating controls listed above while your patch roll‑out proceeds. (msrc.microsoft.com)

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Source: MSRC Security Update Guide - Microsoft Security Response Center