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.

• https://xenbits.xenproject.org/xsa/advisory-511.html
• http://www.openwall.com/lists/oss-security/2026/09/08/8
• http://xenbits.xen.org/xsa/advisory-511.html