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CWE-367Weakness · CWE-367

CVE-2025-58151

CRITICAL · 9.4 CVSS v4.0 Published 2026-07-09
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
99/100
Remediation priority · Urgent
No privileges Zero-click 6 weeks old

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
varstored is a component of the Xapi toolstack handling UEFI Variables for a VM. It has a communication path with OVMF inside the VM involving mapping a buffer prepared by OVMF. Within varstored, there were insufficient compiler barriers, creating TOCTOU issues with data in the shared buffer. The exact vulnerable behaviour depends on the code generated by the compiler. In a build of varstored using default settings, the attacker can control an index used in a jump table.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · moderate confidence

varstored (a Xapi toolstack component handling UEFI Variables for VMs) has insufficient compiler memory barriers creating TOCTOU race conditions in its shared buffer communication with OVMF inside the VM. The lack of memory ordering constraints allows the compiler to reorder operations, enabling an attacker to control a jump table index in default builds, potentially leading to arbitrary code execution.

MitigationApply vendor patches for CVE-2025-58151 to varstored once available. Until patched, restrict VM creation/modification privileges to trusted users and monitor for indicators of compromise targeting the varstored/OVMF communication path.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
Low
Privileges
None
Authentication
X
User interaction
None
Scope
X

CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Confirm varstored is deployed
    Check for varstored process or service running on the host: look for 'varstored' in running processes (ps aux | grep varstored) or check for its binary in typical Xapi toolstack paths
    Affected if varstored is present and handling UEFI variable storage for VMs
  2. Identify OVMF usage
    Check VM configurations to see if they use OVMF firmware (UEFI boot): examine VM config files for OVMF or UEFI firmware settings
    Affected if VMs are configured to use OVMF (OVMF/UEFI) and varstored is managing their UEFI variables
  3. Check shared buffer configuration
    Inspect varstored configuration for shared memory buffer settings between varstored and OVMF: look for parameters defining the shared buffer path or memory region used for communication
    Affected if a shared buffer path exists between varstored and OVMF for UEFI variable communication
  4. Review build for compiler barriers
    Examine varstored binary or source for presence of synchronization primitives (locks, memory barriers) around shared buffer accesses: check if the build includes proper barriers to prevent TOCTOU race conditions
    Affected if the varstored build lacks proper compiler barriers or synchronization around shared buffer operations (default builds are affected)
  5. Verify race condition exposure
    Monitor or inspect the shared buffer handling code path: look for code sections where data is checked then used without atomic operations or proper serialization
    Affected if data in the shared memory region is checked and used non-atomically, allowing potential race condition exploitation

If varstored is handling UEFI variables for OVMF-based VMs using a shared buffer in a default build without proper synchronization primitives, the environment is affected by this TOCTOU vulnerability.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Apply vendor patches for CVE-2025-58151 to varstored once available. Until patched, restrict VM creation/modification privileges to trusted users and monitor for indicators of compromise targeting the varstored/OVMF communication path.

Have this fixed Scoped from the published advisory
  • Consultation4.0 h
  • Implementation12.0 h
  • Testing16.0 h
  • Review / QA6.0 h
38.0 hours of engineering $6,440
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2025-58151 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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