CVE-2025-58151

varstored: TOCTOU issues with mapped guest memory

Published Jul 9, 2026 CVSS 4.0 · 9.4 Critical EPSS < 1% KEV · Not listed
Description
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

No advisories available
History
Type Values Removed Values Added
First Time appeared Xen
Xen varstored
Vendors & Products Xen
Xen varstored
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}

Type Values Removed Values Added
Description 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.
Title varstored: TOCTOU issues with mapped guest memory
Weaknesses CWE-367
References
Metrics cvssV4_0

{'score': 9.4, 'vector': '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'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
XEN
Published
Updated
Jul 9, 2026, 3:41 PM
Reserved
Aug 26, 2025, 6:48 AM
Status
Deferred
Published
Jul 9, 2026, 4:16 PM
Modified
Sep 29, 2026, 7:10 PM