# CVE-2026-99088: net: openvswitch: validate transport header presence in set_ipv6_addr


- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Fix available:** Yes
- **Published:** 26 Oct 2026
- **Updated:** 26 Oct 2026
- **Also known as:** AZL-111119, BELL-CVE-2026-99088, DEBIAN-CVE-2026-99088, GHSA-hwf6-223w-r64q, UBUNTU-CVE-2026-99088

## What is CVE-2026-99088?

CVE-2026-99088 is a vulnerability in Linux, published on 26 Oct 2026. 

### Official description

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

## Which versions are affected by CVE-2026-99088?


## How do I fix CVE-2026-99088?

Upgrade to a fixed version.

## Is CVE-2026-99088 being exploited?

There is no known exploitation of CVE-2026-99088 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-99088 and fix it if it is affected.

What it is: CVE-2026-99088 is a vulnerability in Linux, published on 26 Oct 2026. 
Exploitation: There is no known exploitation of CVE-2026-99088 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-99088/ (Markdown: https://insights.sbomify.com/CVE-2026-99088/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-99088
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-99088
- OSV: https://osv.dev/vulnerability/CVE-2026-99088

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-99088/
Summaries are generated and may contain mistakes; the official description above is the record.