by Kastro
Paper/Archive/CVE-2025-58151

CVE-2025-58151

Xen varstored — varstored: TOCTOU issues with mapped guest memory

EPSS 0.1%CVSS 9.4
critical.is priorityof 100
29
CVSS 9.4 (CNA)9.4 / 10 × 3028.2Not in CISA KEV+300.0EPSS percentile 3.1.031 × 200.6No public exploit+100.0SSVC exploitation: none+100.0
Description · from the CVE record

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

ProductAffectedFixed inSource
varstoredall–CNA

Scores by source

XEN (CNA)9.4CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H
CISA ADPSSVCExploitation: none · Automatable: no · Technical impact: total

References

refxenbits.xen.org/xsa/advisory-478.htmlrefopenwall.com/lists/oss-security/2026/01/27/2refxenbits.xen.org/xsa/advisory-478.html