Bug 2481978 (CVE-2026-45865)

Summary:	CVE-2026-45865 kernel: mctp i2c: initialise event handler read bytes
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security <prodsec-ir-bot>
Status:	NEW ---	QA Contact:
Severity:	unspecified	Docs Contact:
Priority:	unspecified
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 Message Control Transport Protocol (MCTP) over I2C (Inter-Integrated Circuit) implementation. A local attacker could exploit this vulnerability by performing I2C reads on an MCTP-I2C device. This could lead to the disclosure of uninitialized stack memory, potentially revealing sensitive information.	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 2026-05-27 15:05:18 UTC

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

mctp i2c: initialise event handler read bytes

Set a 0xff value for i2c reads of an mctp-i2c device. Otherwise reads
will return "val" from the i2c bus driver. For i2c-aspeed and
i2c-npcm7xx that is a stack uninitialised u8.

Tested with "i2ctransfer -y 1 r10@0x34" where 0x34 is a mctp-i2c
instance, now it returns all 0xff.

Comment 1 Keith Grant 2026-05-28 03:59:24 UTC

Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026052711-CVE-2026-45865-87b8@gregkh/T