Bug 2554835 (CVE-2026-98466)

Summary:	CVE-2026-98466 kernel: KVM: arm64: Transfer the hyp stack pages out of the host stage-2
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security DevOps Team <prodsec-dev>
Status:	NEW ---	QA Contact:
Severity:	high	Docs Contact:
Priority:	high
Version:	unspecified	CC:	akhatavk, aos-team-art-private, asdas, dpaolell, jdelft, jupierce, lgarciaa, mbiarnes, ppalepu, ppostler, prdhamdh, rhel-process-autobot, sghai, sidsharm, suppawar, vlaad, watson-tool-maintainers
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	---
Doc Text:	A flaw was found in the Linux kernel's KVM (Kernel-based Virtual Machine) subsystem on ARM64 platforms. During system initialization in protected virtualization modes, the hypervisor fails to revoke host stage-2 access permissions for per-CPU hypervisor stack memory pages. A privileged local host can exploit this flaw to inspect or alter sensitive hypervisor stack data, resulting in a bypass of hypervisor isolation and potential privilege escalation.	Story Points:	---
Clone Of:		Environment:
Last Closed:		Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2026-10-18 15:21:54 UTC

In the Linux kernel, the following vulnerability has been resolved:

KVM: arm64: Transfer the hyp stack pages out of the host stage-2

fix_host_ownership() walks only the linear-map alias of each memblock
region, and the per-CPU hyp stack, mapped in the private VA range for
its guard page, has none.

Walk each stack's VA range with the same walker.

Comment 1 Mauro Matteo Cascella 2026-10-19 17:50:03 UTC

Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-98466.mbox