Bug 2540567 (CVE-2026-97436)

Summary:	CVE-2026-97436 kernel: dpaa2-switch: rework FDB management on the bridge leave path
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 dpaa2-switch driver. When multiple network bridges are configured across ports on the same switch device, removing a port from a bridge fails to release its Forwarding Database (FDB), which tracks network destination addresses. A privileged user modifying network bridge configurations can trigger this condition, eventually forcing independent switch ports to share the same forwarding table. This issue may lead to improper network packet forwarding and unintended traffic exposure between isolated interfaces.	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 2026-09-24 17:17:40 UTC

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

dpaa2-switch: rework FDB management on the bridge leave path

On bridge leave, the dpaa2_switch_port_set_fdb() function always
allocates a new FDB for the port which is becoming standalone. In case
no FDB is found, then the port leaving a bridge will continue to use the
current one.

The above logic does not cover the case in which there are multiple
bridges which have ports from the same DPSW instance. In this case, when
the last port leaves bridge #1, it finds an unused FDB to switch to, but
the old FDB is not marked as unused. Since the number of FDBs is equal
to the number of DPSW interfaces, this will eventually lead to multiple
ports sharing the same FDB.

Fix this by changing how we are managing the FDBs on the leave path.
Instead of directly allocating a new FDB, first verify if the current
port is the last one to leave a bridge. If this is the case, then
continue to use the current FDB and only allocate another FDB if there
are other ports remaining in the bridge.

Comment 1 Mauro Matteo Cascella 2026-09-29 14:05:52 UTC

Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-97436.mbox