Vulnerability in Xen

CVE-2026-79603

x86 PV guests can free memory pages while still keeping a stale TLB entry pointing to them. A TLB flush is only issued by Xen (if needed) when the page is re-used. Since it's possible for the page to be scrubbed ahead of the TLB flush, there's a window where a PV guest can modify an already scrubbed page.

Published · last modified .

CVSS v3 metric

CVSS v3 base score 4.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N.

EPSS exploit prediction

EPSS: 0.002 (12.1th percentile), scored .

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 12th percentile — 12.1% 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-2026-79603: held from 0.002 to 0.002.

EPSS over last 30 days · oldest: 0.002 · newest: 0.002 · change: -0.000

Affected products

  • Xen — versions consult Xen advisory XSA-511

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2026-79603?
CVE-2026-79603 is a medium-severity vulnerability in Xen, classified under CWE-664. CVSS score: 4.3/10. Published 2026-09-08.
How severe is CVE-2026-79603?
Medium severity. CVSS v3 base score is 4.3 out of 10.