Bug 2502336 (CVE-2026-63938)

Summary:	CVE-2026-63938 kernel: KVM: SEV: Check PSC request indices against the actual size of the buffer
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security <prodsec-ir-bot>
Status:	NEW ---	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	rhel-process-autobot, watson-tool-maintainers
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
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Fixed In Version:		Doc Type:	---
Doc Text:	A flaw was found in the Linux kernel's Kernel-based Virtual Machine (KVM) Secure Encrypted Virtualization (SEV) feature. When processing Page State Change (PSC) requests, the system does not properly validate the PSC buffer against the effective size of the scratch area. This can occur if a guest operating system provides a pointer that is not precisely at the start of the Guest Hypervisor Communication Block (GHCB) shared buffer, potentially leading to out-of-bounds memory access. This vulnerability could allow a malicious guest to cause a denial of service on the host system.	Story Points:	---
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Regression:	---	Mount Type:	---
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oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2026-07-19 16:02:36 UTC

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

KVM: SEV: Check PSC request indices against the actual size of the buffer

When processing Page State Change (PSC) requests, validate the PSC buffer
against the effective size of the scratch area, which could be less than
the maximum size if the guest provided a pointer that isn't exactly at the
start of the GHCB shared buffer.

Comment 1 Keith Grant 2026-07-21 21:50:27 UTC

Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026071952-CVE-2026-63938-2d13@gregkh/T