---
id: "CVE-2026-98532"
kind: "vulnerability"
aliases: ["CVE-2026-98532"]
title: "Linux kernel IPv6: out-of-bounds read and write from malformed extension headers"
severity: "unknown"
cvss: null
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["ipv6", "kubernetes", "linux-kernel", "openvswitch", "package", "self-hosted"]
not_affected_if: ["openvswitch-not-loaded"]
published_at: "2026-10-18T16:17:04+00:00"
first_seen_at: "2026-10-23T21:57:15+00:00"
updated_at: "2026-10-25T05:23:52+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98532", "first_seen_at": "2026-10-23T21:57:15+00:00"}]
---

# Linux kernel IPv6: out-of-bounds read and write from malformed extension headers

The IPv6 extension header walker in the Linux kernel could return an offset past the end of a packet when a header declared a length larger than the packet. Open vSwitch then used that offset to read and write the transport checksum out of bounds, which can corrupt kernel memory.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Run `uname -r` and compare against the fixed kernel builds listed by your distribution's security tracker for CVE-2026-98532
- Check whether the openvswitch module is loaded with `lsmod | grep openvswitch`

## Fix

- Update the Linux kernel to a release that includes the upstream fix for CVE-2026-98532 (exact version unknown from these sources)
- Reboot after the kernel update so the fixed code is running

## Timeline

- 2026-10-23T21:57:15+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-98532

## From the sources

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

ipv6: do not let ipv6_find_hdr() return an offset past the packet end

ipv6_find_hdr() walks the extension header chain, skipping each header by
the length that header itself declares.  ipv6_optlen() returns up to 2048,
and the skip is never checked against skb->len, so the offset stored in
*offset can point past the end of the packet.

openvswitch installs that offset as the transport header, and
update_ipv6_checksum() then reads and writes the transport checksum field
out of bounds:

  BUG: KASAN: slab-use-after-free in inet_proto_csum_replace16+0x445/0x470
  Read of size 2 at addr ffff88810b754b06 by task ovs_ipv6_oob/629
  CPU: 4 UID: 1000 PID: 629 Comm: ovs_ipv6_oob Tainted: G N 7.3.0-rc3+ #348
  Call Trace:
   inet_proto_csum_replace16+0x445/0x470
   set_ipv6_addr+0x3dd/0x460
   do_execute_actions+0x6a3d/0x7c40
   ovs_execute_actions+0xfd/0x480
   ovs_packet_cmd_execute+0xc38/0xf20
   genl_rcv_msg+0x59e/0x870
   netlink_rcv_skb+0x18b/0x450
   genl_rcv+0x2d/0x40
   netlink_unicast+0x6bc/0xa20

  The buggy address belongs to the object at ffff88810b754980
   which belongs to the cache skbuff_small_head of size 704
  The buggy address is located 390 bytes inside of
   freed 704-byte region [ffff88810b754980, ffff88810b754c40)

Other callers use that offset too, so bound it here rather than in one
caller.

Reject a header whose declared length does not fit in the packet.
ipv6_find_hdr() already fails with -EBADMSG on a malformed chain, so this
adds no new failure mode.

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