Vulnerability · Published Jul 9, 2026 · Assigned by XEN
CVE-2025-58151varstored: TOCTOU issues with mapped guest memory
Critical 9.4
In plain English
A critical-severity security flaw in varstored from Xen. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.1% (higher than 3% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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 packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine:v3.20 | xen | 0 | ALPINE-CVE-2025-58151 |
| Alpine:v3.21 | xen | 0 | ALPINE-CVE-2025-58151 |
| Alpine:v3.22 | xen | 0 | ALPINE-CVE-2025-58151 |
| Alpine:v3.23 | xen | 0 | ALPINE-CVE-2025-58151 |
| Alpine:v3.24 | xen | 0 | ALPINE-CVE-2025-58151 |
Affected products (as reported)
Weakness: CWE-367 · 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