CVE-2026-79603
Publication date 8 September 2026
Last updated 10 September 2026
Ubuntu priority
Description
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. Deployments using `xsm=silo scrub-domheap` with the aim of not allowing the exchange of information amongst guests are not effective in the presence of PV guests. All Xen versions from 4.13 onwards are vulnerable. Xen versions 4.12 and earlier are not vulnerable as they lack the `scrub-domheap` command line option. Only x86 PV guests can exploit the vulnerability.
Status
| Package | Ubuntu Release | Status |
|---|---|---|
| xen | 26.04 LTS resolute |
Needs evaluation
|
| 24.04 LTS noble |
Needs evaluation
|
|
| 22.04 LTS jammy |
Needs evaluation
|
|
| 20.04 LTS focal |
Needs evaluation
|
|
| 18.04 LTS bionic |
Needs evaluation
|
|
| 16.04 LTS xenial |
Needs evaluation
|
Notes
mdeslaur
hypervisor packages are in universe. For issues in the hypervisor, add appropriate tags to each section, ex: Tags_xen: universe-binary
Severity score breakdown
CVSS version: CVSS v3.0
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