Bug 2516356 (CVE-2026-72436)

Summary:	CVE-2026-72436 kernel: netfilter: ipset: Don't use test_bit() in lockless RCU readers in hash types
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:	rhel-process-autobot, 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 `netfilter: ipset` component of the Linux kernel. This vulnerability occurs because a specific operation, `test_bit()`, is used in a way that lacks proper safeguards when multiple processes access shared data simultaneously. This can lead to situations where the system processes data incorrectly or behaves unexpectedly. Such issues could potentially result in data corruption or make the system unavailable (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 2026-08-15 06:08:13 UTC

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

netfilter: ipset: Don't use test_bit() in lockless RCU readers in hash types

Sashiko pointed out that there are a few lockless RCU readers
using test_bit() which is a relaxed atomic operation and
provides no memory barrier guarantees. Use test_bit_acquire()
instead where the operation may run parallel with add/del/gc,
i.e. is not one from the next cases

- protected by region lock
- in a set destroy phase
- in a new/temporary set creation phase

Comment 1 gkamathe 2026-08-18 07:50:30 UTC

Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026081528-CVE-2026-72436-eb00@gregkh/T