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CRITICAL

varstored: TOCTOU issues with mapped guest memory

Published Jul 9, 2026

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.

Affected products

Remediation

No remediation recorded yet.

Weaknesses (1)

References (4)

Change history (0)

No recorded changes yet.

Sources
CVE.org / MITRE
Status PUBLISHED
Assigner XEN
Published Jul 9, 2026
Updated Jul 9, 2026
Reserved Aug 26, 2025
CISA Vulnrichment
Updated Jul 9, 2026
NVD
Status Deferred
Modified Jul 9, 2026
Red Hat
Severity n/a
Public date n/a
ENISA EUVD
Assigner XEN
Published Jul 9, 2026
Updated Jul 9, 2026
Exploited since n/a
EUVD-2025-210447