Bug 2550648 (CVE-2026-79610)

Summary: CVE-2026-79610 xen: Xen: Host privilege escalation via stale grant table pointers
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
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Priority: high    
Version: unspecifiedKeywords: Security
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OS: Linux   
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A flaw was found in Xen. When a guest virtual machine repeatedly changes grant table configurations, the hypervisor frees and reallocates status memory pages, rendering previously calculated pointers invalid. A malicious guest can exploit these stale pointers to corrupt hypervisor memory, potentially leading to host privilege escalation or a Denial of Service (DoS) condition.
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Bug Depends On: 2559182    
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Description OSIDB Bzimport 2026-10-13 15:52:18 UTC 
XSA-501 was about issues with v1 -> v2 and v2 -> v1 changes racing certain
other grant table operations.  Sadly a v2 -> v1 -> v2 change has yet
another effect which wasn't accounted for: During the first change, status
pages would be freed.  During the second change they would be allocated
again.  Hence across the full pair of change the addresses of the status
pages may change, rendering stale previously calculated pointers into the
status array.