Bug 2450243 (CVE-2026-23554)

Summary:	CVE-2026-23554 xen: Xen: Information disclosure and potential privilege escalation via use-after-free in EPT paging
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security <prodsec-ir-bot>
Status:	NEW ---	QA Contact:
Severity:	high	Docs Contact:
Priority:	high
Version:	unspecified	Keywords:	Security
Target Milestone:	---
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Hardware:	All
OS:	Linux
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Fixed In Version:		Doc Type:	---
Doc Text:	A flaw was found in Xen. An optimization in the Intel Extended Page Table (EPT) paging code, used by Xen, defers flushing cached EPT state. However, the freeing of paging structures is not similarly deferred. This can result in freed memory pages remaining in the cached state, allowing stale entries to point to memory regions not intended for guest access. A malicious guest could potentially exploit this to access unintended memory regions, leading to information disclosure or privilege escalation.	Story Points:	---
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oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:	2450273
Bug Blocks:

Description OSIDB Bzimport 2026-03-23 08:01:45 UTC

The Intel EPT paging code uses an optimization to defer flushing of any cached
EPT state until the p2m lock is dropped, so that multiple modifications done
under the same locked region only issue a single flush.

Freeing of paging structures however is not deferred until the flushing is
done, and can result in freed pages transiently being present in cached state.
Such stale entries can point to memory ranges not owned by the guest, thus
allowing access to unintended memory regions.