Bug 2464351 (CVE-2026-43037) - CVE-2026-43037 kernel: ip6_tunnel: clear skb2->cb[] in ip4ip6_err()
Summary: CVE-2026-43037 kernel: ip6_tunnel: clear skb2->cb[] in ip4ip6_err()
Keywords:
Status: NEW
Alias: CVE-2026-43037
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
urgent
urgent
Target Milestone: ---
Assignee: Product Security
QA Contact:
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2026-05-01 15:01 UTC by OSIDB Bzimport
Modified: 2026-06-19 15:01 UTC (History)
2 users (show)

Fixed In Version:
Clone Of:
Environment:
Last Closed:
Embargoed:

Attachments (Terms of Use)


Links
System ID Private Priority Status Summary Last Updated
Red Hat Product Errata RHSA-2026:22900 0 None None None 2026-06-03 15:19:25 UTC
Red Hat Product Errata RHSA-2026:22940 0 None None None 2026-06-03 19:17:53 UTC
Red Hat Product Errata RHSA-2026:22964 0 None None None 2026-06-04 15:45:49 UTC
Red Hat Product Errata RHSA-2026:23224 0 None None None 2026-06-04 12:16:37 UTC
Red Hat Product Errata RHSA-2026:23237 0 None None None 2026-06-04 10:22:42 UTC
Red Hat Product Errata RHSA-2026:24343 0 None None None 2026-06-08 03:03:29 UTC
Red Hat Product Errata RHSA-2026:25044 0 None None None 2026-06-18 15:07:57 UTC
Red Hat Product Errata RHSA-2026:25120 0 None None None 2026-06-10 20:00:19 UTC
Red Hat Product Errata RHSA-2026:25121 0 None None None 2026-06-10 21:39:05 UTC
Red Hat Product Errata RHSA-2026:25181 0 None None None 2026-06-17 17:17:39 UTC
Red Hat Product Errata RHSA-2026:25186 0 None None None 2026-06-16 13:46:59 UTC
Red Hat Product Errata RHSA-2026:25191 0 None None None 2026-06-11 06:49:32 UTC
Red Hat Product Errata RHSA-2026:25193 0 None None None 2026-06-16 10:10:40 UTC
Red Hat Product Errata RHSA-2026:25200 0 None None None 2026-06-17 09:37:57 UTC
Red Hat Product Errata RHSA-2026:25217 0 None None None 2026-06-11 10:13:30 UTC
Red Hat Product Errata RHSA-2026:25533 0 None None None 2026-06-12 19:51:46 UTC
Red Hat Product Errata RHSA-2026:25534 0 None None None 2026-06-12 19:47:48 UTC
Red Hat Product Errata RHSA-2026:26535 0 None None None 2026-06-17 09:18:45 UTC

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
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