Bug 2464369 (CVE-2026-43027)

Summary:	CVE-2026-43027 kernel: netfilter: nf_conntrack_helper: pass helper to expect cleanup
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security <prodsec-ir-bot>
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 Linux kernel's netfilter subsystem, specifically within the `nf_conntrack_helper`. When a connection tracking helper is unregistered, its associated expectations are not properly cleaned up. This oversight can lead to a use-after-free vulnerability, where the system attempts to access memory that has already been released. A local attacker could exploit this to cause a system crash, resulting in a Denial of Service (DoS), or potentially achieve privilege escalation.	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 2026-05-01 15:02:48 UTC

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

netfilter: nf_conntrack_helper: pass helper to expect cleanup

nf_conntrack_helper_unregister() calls nf_ct_expect_iterate_destroy()
to remove expectations belonging to the helper being unregistered.
However, it passes NULL instead of the helper pointer as the data
argument, so expect_iter_me() never matches any expectation and all
of them survive the cleanup.

After unregister returns, nfnl_cthelper_del() frees the helper
object immediately.  Subsequent expectation dumps or packet-driven
init_conntrack() calls then dereference the freed exp->helper,
causing a use-after-free.

Pass the actual helper pointer so expectations referencing it are
properly destroyed before the helper object is freed.

  BUG: KASAN: slab-use-after-free in string+0x38f/0x430
  Read of size 1 at addr ffff888003b14d20 by task poc/103
  Call Trace:
   string+0x38f/0x430
   vsnprintf+0x3cc/0x1170
   seq_printf+0x17a/0x240
   exp_seq_show+0x2e5/0x560
   seq_read_iter+0x419/0x1280
   proc_reg_read+0x1ac/0x270
   vfs_read+0x179/0x930
   ksys_read+0xef/0x1c0
  Freed by task 103:
  The buggy address is located 32 bytes inside of
   freed 192-byte region [ffff888003b14d00, ffff888003b14dc0)

Comment 1 Keith Grant 2026-05-01 17:12:00 UTC

Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026050159-CVE-2026-43027-5711@gregkh/T

Comment 3 errata-xmlrpc 2026-05-28 01:19:56 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 10

Via RHSA-2026:21557 https://access.redhat.com/errata/RHSA-2026:21557

Comment 4 errata-xmlrpc 2026-05-28 01:24:02 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9

Via RHSA-2026:21556 https://access.redhat.com/errata/RHSA-2026:21556

Comment 5 errata-xmlrpc 2026-05-28 08:26:02 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8

Via RHSA-2026:21706 https://access.redhat.com/errata/RHSA-2026:21706

Comment 6 errata-xmlrpc 2026-05-28 13:26:29 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8

Via RHSA-2026:21745 https://access.redhat.com/errata/RHSA-2026:21745

Comment 7 errata-xmlrpc 2026-07-01 08:59:01 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9.6 Extended Update Support

Via RHSA-2026:34094 https://access.redhat.com/errata/RHSA-2026:34094

Comment 8 errata-xmlrpc 2026-07-08 14:51:28 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions

Via RHSA-2026:36767 https://access.redhat.com/errata/RHSA-2026:36767

Comment 9 errata-xmlrpc 2026-07-14 16:41:13 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 10.0 Extended Update Support

Via RHSA-2026:39371 https://access.redhat.com/errata/RHSA-2026:39371

Comment 10 errata-xmlrpc 2026-07-15 13:41:25 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions

Via RHSA-2026:39983 https://access.redhat.com/errata/RHSA-2026:39983

Comment 11 errata-xmlrpc 2026-07-15 15:54:14 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support
  Red Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-On

Via RHSA-2026:40068 https://access.redhat.com/errata/RHSA-2026:40068

Comment 12 errata-xmlrpc 2026-07-15 16:03:11 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions

Via RHSA-2026:40082 https://access.redhat.com/errata/RHSA-2026:40082

Comment 13 errata-xmlrpc 2026-07-16 07:16:17 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions
  Red Hat Enterprise Linux 8.8 Telecommunications Update Service

Via RHSA-2026:40760 https://access.redhat.com/errata/RHSA-2026:40760

Comment 14 errata-xmlrpc 2026-07-29 01:06:29 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support
  Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On

Via RHSA-2026:47633 https://access.redhat.com/errata/RHSA-2026:47633