Bug 2464351 (CVE-2026-43037)

Summary:	CVE-2026-43037 kernel: ip6_tunnel: clear skb2->cb[] in ip4ip6_err()
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security <prodsec-ir-bot>
Status:	NEW ---	QA Contact:
Severity:	urgent	Docs Contact:
Priority:	urgent
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 IPv6 tunnel implementation. A remote attacker could exploit this flaw by sending malicious ICMPv6 error messages to cause a stack-based buffer overflow in the kernel's IPv4-over-IPv6 tunnel error handling code. This could result in a kernel crash (denial of service) or potentially allow arbitrary code execution with kernel privileges.	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 15:01:43 UTC

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

ip6_tunnel: clear skb2->cb[] in ip4ip6_err()

Oskar Kjos reported the following problem.

ip4ip6_err() calls icmp_send() on a cloned skb whose cb[] was written
by the IPv6 receive path as struct inet6_skb_parm. icmp_send() passes
IPCB(skb2) to __ip_options_echo(), which interprets that cb[] region
as struct inet_skb_parm (IPv4). The layouts differ: inet6_skb_parm.nhoff
at offset 14 overlaps inet_skb_parm.opt.rr, producing a non-zero rr
value. __ip_options_echo() then reads optlen from attacker-controlled
packet data at sptr[rr+1] and copies that many bytes into dopt->__data,
a fixed 40-byte stack buffer (IP_OPTIONS_DATA_FIXED_SIZE).

To fix this we clear skb2->cb[], as suggested by Oskar Kjos.

Also add minimal IPv4 header validation (version == 4, ihl >= 5).

Comment 1 Keith Grant 2026-05-01 17:47:50 UTC

Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026050102-CVE-2026-43037-0346@gregkh/T

Comment 3 errata-xmlrpc 2026-06-03 15:19:25 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions

Via RHSA-2026:22900 https://access.redhat.com/errata/RHSA-2026:22900

Comment 4 errata-xmlrpc 2026-06-03 19:17:52 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions

Via RHSA-2026:22940 https://access.redhat.com/errata/RHSA-2026:22940

Comment 5 errata-xmlrpc 2026-06-04 10:22:41 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions

Via RHSA-2026:23237 https://access.redhat.com/errata/RHSA-2026:23237

Comment 6 errata-xmlrpc 2026-06-04 12:16:36 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9.6 Extended Update Support

Via RHSA-2026:23224 https://access.redhat.com/errata/RHSA-2026:23224

Comment 7 errata-xmlrpc 2026-06-04 15:45:48 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-2026:22964 https://access.redhat.com/errata/RHSA-2026:22964

Comment 8 errata-xmlrpc 2026-06-08 03:03:28 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 10.0 Extended Update Support

Via RHSA-2026:24343 https://access.redhat.com/errata/RHSA-2026:24343

Comment 10 errata-xmlrpc 2026-06-10 20:00:18 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8

Via RHSA-2026:25120 https://access.redhat.com/errata/RHSA-2026:25120

Comment 11 errata-xmlrpc 2026-06-10 21:39:04 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8

Via RHSA-2026:25121 https://access.redhat.com/errata/RHSA-2026:25121

Comment 12 errata-xmlrpc 2026-06-11 06:49:31 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 10

Via RHSA-2026:25191 https://access.redhat.com/errata/RHSA-2026:25191

Comment 13 errata-xmlrpc 2026-06-11 10:13:29 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9

Via RHSA-2026:25217 https://access.redhat.com/errata/RHSA-2026:25217

Comment 14 errata-xmlrpc 2026-06-12 19:47:47 UTC

This issue has been addressed in the following products:

  NVIDIA for RHEL 10

Via RHSA-2026:25534 https://access.redhat.com/errata/RHSA-2026:25534

Comment 15 errata-xmlrpc 2026-06-12 19:51:45 UTC

This issue has been addressed in the following products:

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

Via RHSA-2026:25533 https://access.redhat.com/errata/RHSA-2026:25533

Comment 16 errata-xmlrpc 2026-06-16 10:10:39 UTC

This issue has been addressed in the following products:

  Red Hat OpenShift Container Platform 4.20

Via RHSA-2026:25193 https://access.redhat.com/errata/RHSA-2026:25193

Comment 17 errata-xmlrpc 2026-06-16 13:46:58 UTC

This issue has been addressed in the following products:

  Red Hat OpenShift Container Platform 4.21

Via RHSA-2026:25186 https://access.redhat.com/errata/RHSA-2026:25186

Comment 18 errata-xmlrpc 2026-06-17 09:18:44 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-2026:26535 https://access.redhat.com/errata/RHSA-2026:26535

Comment 19 errata-xmlrpc 2026-06-17 09:37:56 UTC

This issue has been addressed in the following products:

  Red Hat OpenShift Container Platform 4.19

Via RHSA-2026:25200 https://access.redhat.com/errata/RHSA-2026:25200

Comment 20 errata-xmlrpc 2026-06-17 17:17:38 UTC

This issue has been addressed in the following products:

  Red Hat OpenShift Container Platform 4.18

Via RHSA-2026:25181 https://access.redhat.com/errata/RHSA-2026:25181

Comment 21 errata-xmlrpc 2026-06-18 15:07:56 UTC

This issue has been addressed in the following products:

  Red Hat OpenShift Container Platform 4.16

Via RHSA-2026:25044 https://access.redhat.com/errata/RHSA-2026:25044

Comment 23 errata-xmlrpc 2026-06-22 02:40:22 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 6 Extended Lifecycle Support  - EXTENSION

Via RHSA-2026:27719 https://access.redhat.com/errata/RHSA-2026:27719

Comment 24 errata-xmlrpc 2026-06-22 04:26:56 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 7 Extended Lifecycle Support

Via RHSA-2026:27729 https://access.redhat.com/errata/RHSA-2026:27729

Comment 25 errata-xmlrpc 2026-06-24 04:04:21 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions

Via RHSA-2026:28738 https://access.redhat.com/errata/RHSA-2026:28738

Comment 26 errata-xmlrpc 2026-06-24 04:07:21 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 10

Via RHSA-2026:28742 https://access.redhat.com/errata/RHSA-2026:28742

Comment 27 errata-xmlrpc 2026-06-24 04:20:25 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9.6 Extended Update Support

Via RHSA-2026:28740 https://access.redhat.com/errata/RHSA-2026:28740

Comment 28 errata-xmlrpc 2026-06-24 04:20:42 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions

Via RHSA-2026:28750 https://access.redhat.com/errata/RHSA-2026:28750

Comment 29 errata-xmlrpc 2026-06-24 04:23:25 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions

Via RHSA-2026:28748 https://access.redhat.com/errata/RHSA-2026:28748

Comment 30 errata-xmlrpc 2026-06-24 04:25:40 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9

Via RHSA-2026:28741 https://access.redhat.com/errata/RHSA-2026:28741

Comment 31 errata-xmlrpc 2026-06-24 04:33:09 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8

Via RHSA-2026:28749 https://access.redhat.com/errata/RHSA-2026:28749

Comment 32 errata-xmlrpc 2026-06-25 08:38:43 UTC

This issue has been addressed in the following products:

  Red Hat OpenShift Container Platform 4.12

Via RHSA-2026:26528 https://access.redhat.com/errata/RHSA-2026:26528

Comment 33 errata-xmlrpc 2026-06-25 10:38:50 UTC

This issue has been addressed in the following products:

  Red Hat OpenShift Container Platform 4.13

Via RHSA-2026:26542 https://access.redhat.com/errata/RHSA-2026:26542

Comment 34 errata-xmlrpc 2026-06-30 11:28:36 UTC

This issue has been addressed in the following products:

  NVIDIA for RHEL 10

Via RHSA-2026:33486 https://access.redhat.com/errata/RHSA-2026:33486

Comment 35 errata-xmlrpc 2026-07-01 11:16:13 UTC

This issue has been addressed in the following products:

  Red Hat OpenShift Container Platform 4.14

Via RHSA-2026:28887 https://access.redhat.com/errata/RHSA-2026:28887

Comment 36 errata-xmlrpc 2026-07-06 12:51:38 UTC

This issue has been addressed in the following products:

  Red Hat OpenShift Container Platform 4.15

Via RHSA-2026:28962 https://access.redhat.com/errata/RHSA-2026:28962

Comment 37 errata-xmlrpc 2026-07-09 08:03:00 UTC

This issue has been addressed in the following products:

  Red Hat OpenShift Container Platform 4.17

Via RHSA-2026:34098 https://access.redhat.com/errata/RHSA-2026:34098

Comment 38 errata-xmlrpc 2026-07-17 12:52:27 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 7 Extended Lifecycle Support

Via RHSA-2026:41236 https://access.redhat.com/errata/RHSA-2026:41236

Comment 39 errata-xmlrpc 2026-07-28 11:46:55 UTC

This issue has been addressed in the following products:

  Red Hat OpenShift Container Platform 4.22

Via RHSA-2026:44232 https://access.redhat.com/errata/RHSA-2026:44232