Bug 2536595 (CVE-2026-90094)

Summary:	CVE-2026-90094 kernel: arm64: process: Fix context switching MTE store-only tag check
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:	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, affecting the arm64 architecture's process context switching. When a user enables the Memory Tagging Extension (MTE) store-only tag check mode, the associated security setting (SCTLR_EL1.TCSO0) is not properly reset during a task switch. This oversight allows the MTE setting to be inadvertently exposed to another task. Such a leakage could potentially lead to unintended information disclosure or a bypass of security isolation mechanisms.	Story Points:	---
Clone Of:		Environment:
Last Closed:		Type:	---
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Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2026-09-17 18:38:29 UTC

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

arm64: process: Fix context switching MTE store-only tag check

SCTLR_EL1.TCSO0 is set when user opt-in for MTE store-only tag check
mode. However, it is not part of SCTLR_USER_MASK which imply that on
context switch we never clear SCTLR_EL1.TCSO0, so we are leaking that
setting into another task.

Fix that by including SCTLR_EL1_TCSO0_MASK into SCTLR_USER_MASK

Comment 1 Keith Grant 2026-09-22 20:39:53 UTC

Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-90094.mbox