---
id: CVE-2026-99088
title: 'net: openvswitch: validate transport header presence in set_ipv6_addr'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  net: openvswitch: validate transport header presence in set_ipv6_addr

  When executing IPv6 address rewrite actions on IPv6 fragments,
  set_ipv6_addr() calls update_ipv6_…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 3fdbd1ce11e5c0d7cafbe44c942c5cad61113d7b <
    b7b80d204abdc258006f9e17c92b363ab13bb599
  - >-
    Linux >= 3fdbd1ce11e5c0d7cafbe44c942c5cad61113d7b <
    6774af7cd17be8f0d0f70de3a749d381b4f2e9da
  - >-
    Linux >= 3fdbd1ce11e5c0d7cafbe44c942c5cad61113d7b <
    2594795fd832f0253826d64ff8976b8ff5fbfe9f
  - >-
    Linux >= 3fdbd1ce11e5c0d7cafbe44c942c5cad61113d7b <
    6b8897ba0733f88f0360ea48a970f373f9142de0
  - >-
    Linux >= 3fdbd1ce11e5c0d7cafbe44c942c5cad61113d7b <
    3c6a4b11330fe424557538a98fca9f0a4c5bf313
  - Linux 3.8
published: '2026-10-26'
updated: '2026-10-26'
sourceUpdated: '2026-10-26T14:51:58.460Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-99088'
references:
  - url: 'https://git.kernel.org/stable/c/b7b80d204abdc258006f9e17c92b363ab13bb599'
  - url: 'https://git.kernel.org/stable/c/6774af7cd17be8f0d0f70de3a749d381b4f2e9da'
  - url: 'https://git.kernel.org/stable/c/2594795fd832f0253826d64ff8976b8ff5fbfe9f'
  - url: 'https://git.kernel.org/stable/c/6b8897ba0733f88f0360ea48a970f373f9142de0'
  - url: 'https://git.kernel.org/stable/c/3c6a4b11330fe424557538a98fca9f0a4c5bf313'
tags:
  - cve.org
ingestedAt: '2026-10-26T15:29:30.508Z'
---

## Overview

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

net: openvswitch: validate transport header presence in set_ipv6_addr

When executing IPv6 address rewrite actions on IPv6 fragments,
set_ipv6_addr() calls update_ipv6_checksum(). If parse_ipv6hdr()
processes a non-first IPv6 fragment, it sets key->ip.proto to
NEXTHDR_FRAGMENT and returns early without calling
skb_set_transport_header().

update_ipv6_checksum() unconditionally evaluates skb_transport_offset()
on entry before checking l4_proto.  Because skb->transport_header is
uninitialized, this triggers a warning under CONFIG_DEBUG_NET=y although
it is completely harmless.

Fix this by returning early in update_ipv6_checksum() if l4_proto is
NEXTHDR_FRAGMENT. This avoids reading the uninitialized transport offset
for fragments while preserving the debug warning for any other protocol
where the transport header is unexpectedly missing.

See the syzbot trace:

!skb_transport_header_was_set(skb)
WARNING: ./include/linux/skbuff.h:3075 at skb_transport_header include/linux/skbuff.h:3075 [inline], CPU#1: syz-executor463/5635
WARNING: ./include/linux/skbuff.h:3075 at skb_transport_offset include/linux/skbuff.h:3250 [inline], CPU#1: syz-executor463/5635
WARNING: ./include/linux/skbuff.h:3075 at update_ipv6_checksum net/openvswitch/actions.c:361 [inline], CPU#1: syz-executor463/5635
WARNING: ./include/linux/skbuff.h:3075 at set_ipv6_addr+0x462/0x660 net/openvswitch/actions.c:399, CPU#1: syz-executor463/5635
[...]
RIP: 0010:skb_transport_header include/linux/skbuff.h:3075 [inline]
RIP: 0010:skb_transport_offset include/linux/skbuff.h:3250 [inline]
RIP: 0010:update_ipv6_checksum net/openvswitch/actions.c:361 [inline]
RIP: 0010:set_ipv6_addr+0x462/0x660 net/openvswitch/actions.c:399
[...]
Call Trace:
 <TASK>
 set_ipv6 net/openvswitch/actions.c:531 [inline]
 do_execute_actions+0x557e/0x8600 net/openvswitch/actions.c:1366
 ovs_execute_actions+0xde/0x520 net/openvswitch/actions.c:1592
 ovs_packet_cmd_execute+0xb4f/0xf10 net/openvswitch/datapath.c:705
 genl_family_rcv_msg_doit+0x233/0x340 net/netlink/genetlink.c:1114
 genl_rcv_msg+0x614/0x7a0 net/netlink/genetlink.c:1209
 netlink_rcv_skb+0x226/0x4a0 net/netlink/af_netlink.c:2572
 genl_rcv+0x28/0x40 net/netlink/genetlink.c:1218
 netlink_unicast+0x7bd/0x940 net/netlink/af_netlink.c:1361
 netlink_sendmsg+0x813/0xb40 net/netlink/af_netlink.c:1916
 sock_sendmsg_nosec+0x14e/0x190 net/socket.c:800

## Affected

- `Linux >= 3fdbd1ce11e5c0d7cafbe44c942c5cad61113d7b < b7b80d204abdc258006f9e17c92b363ab13bb599`
- `Linux >= 3fdbd1ce11e5c0d7cafbe44c942c5cad61113d7b < 6774af7cd17be8f0d0f70de3a749d381b4f2e9da`
- `Linux >= 3fdbd1ce11e5c0d7cafbe44c942c5cad61113d7b < 2594795fd832f0253826d64ff8976b8ff5fbfe9f`
- `Linux >= 3fdbd1ce11e5c0d7cafbe44c942c5cad61113d7b < 6b8897ba0733f88f0360ea48a970f373f9142de0`
- `Linux >= 3fdbd1ce11e5c0d7cafbe44c942c5cad61113d7b < 3c6a4b11330fe424557538a98fca9f0a4c5bf313`
- `Linux 3.8`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.