varstored: TOCTOU issues with mapped guest memory

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Summary

CVECVE-2025-58151
StatePUBLISHED
AssignerXEN
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-07-09 16:16:33 UTC
Updated2026-07-09 17:16:56 UTC
Descriptionvarstored 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.

Risk And Classification

Primary CVSS: v4.0 9.4 CRITICAL from [email protected]

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

EPSS: 0.001200000 probability, percentile 0.021450000 (date 2026-07-12)

Problem Types: CWE-367 | CWE-367 CWE-367 Time-of-check time-of-use (TOCTOU) race condition

VersionSourceTypeScoreSeverityVector
4.0[email protected]Secondary9.4CRITICALCVSS: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/C...
4.0CNACVSS9.4CRITICALCVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H

CVSS v4.0 Breakdown

Attack Vector
Local
Attack Complexity
Low
Attack Requirements
None
Privileges Required
None
User Interaction
None
Confidentiality
High
Integrity
High
Availability
High
Sub Conf.
High
Sub Integrity
High
Sub Availability
High

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Xen Varstored affected all Linux

References

ReferenceSourceLinkTags
xenbits.xen.org/xsa/advisory-478.html [email protected] xenbits.xen.org
xenbits.xen.org/xsa/advisory-478.html af854a3a-2127-422b-91ae-364da2661108 xenbits.xen.org
www.openwall.com/lists/oss-security/2026/01/27/2 af854a3a-2127-422b-91ae-364da2661108 www.openwall.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: This issue was discovered by Teddy Astie of Vates. (en)

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