CVE-2025-58151

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.