Bug 2536709 (CVE-2026-90306)

Summary:	CVE-2026-90306 kernel: ARM: 9481/2: breakpoint: CFI breakpoints only on demand
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security <prodsec-ir-bot>
Status:	NEW ---	QA Contact:
Severity:	low	Docs Contact:
Priority:	low
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 ARM architecture. When Control-Flow Integrity (CFI) is not actively used, or when a breakpoint is issued in userspace, the hw_breakpoint_cfi_handler() does not properly handle breakpoint type 0x03 (ARM_ENTRY_CFI_BREAKPOINT). This can lead to an unhandled fault, potentially allowing userspace to utilize a breakpoint type intended for kernel-level CFI, which could result in unexpected system behavior 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 19:13:06 UTC

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

ARM: 9481/2: breakpoint: CFI breakpoints only on demand

This removes the stub hw_breakpoint_cfi_handler() from ARM, making
it not steal breakpoint type 0x03 (ARM_ENTRY_CFI_BREAKPOINT) unless
CFI is actively used in the kernel.

When not instrumenting with CFI, or when a breakpoint is issued in
userspace, we fall through to return 1 from hw_breakpoint_pending()
"unhandled fault" so userspace can make use of this breakpoint.

Tested with LKDTM and this command line:
echo CFI_FORWARD_PROTO > /sys/kernel/debug/provoke-crash/DIRECT
still works as expected.

Comment 1 gkamathe 2026-09-23 04:38:03 UTC

Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-90306.mbox