CVE-2026-99088

net: openvswitch: validate transport header presence in set_ipv6_addr

Published Oct 26, 2026 · Updated Oct 26, 2026

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

CVSS severityUnavailable

Unscored

EPSS probability0.17%

Next 30 days · Nov 1, 2026

Known exploitationUnconfirmed

Based on sourced intelligence

Hinoki checkNot available

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Summary

What happened

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: 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

The record

CVE: CVE-2026-99088
Published: Oct 26, 2026
Updated: Oct 26, 2026

Vendor: The Linux Kernel Organization
Product: Linux
Classifications: Unavailable

Attack vector: Unavailable
Privileges: Unavailable

Timeline

How it unfolded

Oct 26, 2026CVE publishedPublication date reported by the CVE source.
Oct 26, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

Affected versionversion=3.8
Affected versionversion=3fdbd1ce11e5c0d7cafbe44c942c5cad61113d7b <2594795fd832f0253826d64ff8976b8ff5fbfe9f
Affected versionversion=3fdbd1ce11e5c0d7cafbe44c942c5cad61113d7b <3c6a4b11330fe424557538a98fca9f0a4c5bf313
Affected versionversion=3fdbd1ce11e5c0d7cafbe44c942c5cad61113d7b <6774af7cd17be8f0d0f70de3a749d381b4f2e9da
Affected versionversion=3fdbd1ce11e5c0d7cafbe44c942c5cad61113d7b <6b8897ba0733f88f0360ea48a970f373f9142de0
Affected versionversion=3fdbd1ce11e5c0d7cafbe44c942c5cad61113d7b <b7b80d204abdc258006f9e17c92b363ab13bb599

What conditions does exploitation require?

Attack vectorUnavailable in this record.

Required privilegesUnavailable in this record.

What is affected?

The Linux Kernel Organization · Linuxversion=3.8; version=3fdbd1ce11e5c0d7cafbe44c942c5cad61113d7b <2594795fd832f0253826d64ff8976b8ff5fbfe9f; version=3fdbd1ce11e5c0d7cafbe44c942c5cad61113d7b <3c6a4b11330fe424557538a98fca9f0a4c5bf313; version=3fdbd1ce11e5c0d7cafbe44c942c5cad61113d7b <6774af7cd17be8f0d0f70de3a749d381b4f2e9da; version=3fdbd1ce11e5c0d7cafbe44c942c5cad61113d7b <6b8897ba0733f88f0360ea48a970f373f9142de0; version=3fdbd1ce11e5c0d7cafbe44c942c5cad61113d7b <b7b80d204abdc258006f9e17c92b363ab13bb599

Published CVSS scores

No CVSS assessment is available in this record.

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Activity data is delayed. The latest report is Sep 28, 2026.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 22, 2026Sep 28, 2026

Latest reporting daySep 28, 2026

Latest daily unique IPsUnavailable

Prior 30-day averageUnavailable

SourceShadowserver honeypots (KEV)

VectorUnavailable

PrivilegesUnavailable

Known exploitationUnconfirmed

Public exploitUnconfirmed

Weakness, pattern, technique

No sourced classifications are available.

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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