Vulnerability in Xen

CVE-2026-42487

HVM guest I/O port accesses are subject to either emulation or at least translation. Translations are managed by the device model (via XEN_DOMCTL_ioport_mapping), and hence the linked list used may changed at any time. Traversal of those lists (while handling guest I/O port accesses) therefore needs synchronizing with updates, which was missing so far.

Vulnerability class: Race Condition

Published · last modified .

CVSS v3 metric

CVSS v3 base score 7.9 (High). Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:H.

EPSS exploit prediction

EPSS: 0.001 (1.8th percentile), scored .

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 2nd percentile — 1.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2026-42487: held from 0.001 to 0.001.

EPSS over last 30 days · oldest: 0.001 · newest: 0.001 · change: +0.000

Affected products

  • Xen — versions consult Xen advisory XSA-491

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2026-42487?
CVE-2026-42487 is a high-severity vulnerability in Xen, classified under Concurrent Execution using Shared Resource with Improper Synchronization (Race Condition). CVSS score: 7.9/10. Published 2026-06-18.
How severe is CVE-2026-42487?
High severity. CVSS v3 base score is 7.9 out of 10.