Bug 2536502 (CVE-2026-90191)

Summary:	CVE-2026-90191 kernel: mailbox: riscv-sbi-mpxy: validate RPMI notification lengths
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security DevOps Team <prodsec-dev>
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's `mailbox: riscv-sbi-mpxy` component. This vulnerability arises from insufficient validation of the SBI (System Binary Interface) return value, which dictates the number of bytes copied from shared memory into the RPMI (RISC-V Platform Management Interface) notification buffer. An attacker could exploit this by providing a malformed notification length, leading to memory corruption. This could result in information disclosure, system instability, or a denial of service.	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 2026-09-17 18:14:28 UTC

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

mailbox: riscv-sbi-mpxy: validate RPMI notification lengths

The SBI return value controls how many bytes are copied from shared
memory into the RPMI notification buffer. It is not validated against
the negotiated shared-memory size before that copy. The event walker
also uses a reversed loop condition and can inspect a short event record.

Validate the complete notification length before copying it, iterate only
while a full event header remains, and stop when a declared event payload
extends beyond the copied notification data.

Comment 1 Keith Grant 2026-09-23 21:59:24 UTC

Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-90191.mbox