Bug 2529764 (CVE-2026-79603)

Summary: CVE-2026-79603 xen: Xen: PV guests can modify scrubbed memory pages due to stale TLB entries
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
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Version: unspecifiedKeywords: Security
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OS: Linux   
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A flaw was found in Xen. x86 paravirtualized (PV) guests can free memory pages while a stale Translation Lookaside Buffer (TLB) entry still points to them. This creates a window where a PV guest can modify a page after it has been scrubbed (cleared) but before the TLB is flushed. This could lead to data integrity issues within the hypervisor.
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Bug Depends On: 2529852    
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Description OSIDB Bzimport 2026-09-08 12:46:44 UTC 
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.