---
id: CVE-2026-23011
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  ipv4: ip_gre: make ipgre_header() robust

  Analog to commit db5b4e39c4e6 ("ip6_gre: make ip6gre_header() robust")

  Over the years, syzbot found many ways to crash the ke…
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  ipv4: ip_gre: make ipgre_header() robust

  Analog to commit db5b4e39c4e6 ("ip6_gre: make ip6gre_header() robust")

  Over the years, syzbot found many ways to crash the ke…
severity: medium
cvss: 5.5
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'
vendor: linux
product: linux_kernel
affected:
  - 'linux_kernel >= 3.10.1, < 5.10.249'
  - 'linux_kernel >= 5.11, < 5.15.199'
  - 'linux_kernel >= 5.16, < 6.1.162'
  - 'linux_kernel >= 6.2, < 6.6.122'
  - 'linux_kernel >= 6.7, < 6.12.67'
  - 'linux_kernel >= 6.13, < 6.18.7'
  - linux_kernel = 3.10
  - linux_kernel = 6.19
patched:
  - linux_kernel 6.18.7
published: '2026-01-25'
updated: '2026-10-15'
sourceUpdated: '2026-10-15T02:18:39.873'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-23011'
references:
  - url: 'https://git.kernel.org/stable/c/06fe0801396a36cab865b34f666de1d65bc5ce8e'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/2ecf0aa7cc262472a9599cc51ba02ada0897a17a'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/554201ed0a8f4d32e719f42caeaeb2735a9ed6ca'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/8d5b6b2d79c1c22a5b0db1187a6439dff375a022'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/aa57bfea4674e6da8104fa3a37760a6f5f255dad'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/e67c577d89894811ce4dcd1a9ed29d8b63476667'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/eeb9a521de40c6fadccc12fa5205e5a1b364d5a8'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://cert-portal.siemens.com/productcert/html/ssa-019113.html'
    label: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e
  - url: 'https://cert-portal.siemens.com/productcert/html/ssa-457936.html'
    label: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e
tags:
  - nvd
  - cve.org
epss: 0.0021
epssPercentile: 0.11098
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-06-10T20:40:53.431859Z'
ingestedAt: '2026-09-08T15:33:26.994Z'
---

## Overview

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

ipv4: ip_gre: make ipgre_header() robust

Analog to commit db5b4e39c4e6 ("ip6_gre: make ip6gre_header() robust")

Over the years, syzbot found many ways to crash the kernel
in ipgre_header() [1].

This involves team or bonding drivers ability to dynamically
change their dev->needed_headroom and/or dev->hard_header_len

In this particular crash mld_newpack() allocated an skb
with a too small reserve/headroom, and by the time mld_sendpack()
was called, syzbot managed to attach an ipgre device.

[1]
skbuff: skb_under_panic: text:ffffffff89ea3cb7 len:2030915468 put:2030915372 head:ffff888058b43000 data:ffff887fdfa6e194 tail:0x120 end:0x6c0 dev:team0
 kernel BUG at net/core/skbuff.c:213 !
Oops: invalid opcode: 0000 [#1] SMP KASAN PTI
CPU: 1 UID: 0 PID: 1322 Comm: kworker/1:9 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Workqueue: mld mld_ifc_work
 RIP: 0010:skb_panic+0x157/0x160 net/core/skbuff.c:213
Call Trace:
 <TASK>
  skb_under_panic net/core/skbuff.c:223 [inline]
  skb_push+0xc3/0xe0 net/core/skbuff.c:2641
  ipgre_header+0x67/0x290 net/ipv4/ip_gre.c:897
  dev_hard_header include/linux/netdevice.h:3436 [inline]
  neigh_connected_output+0x286/0x460 net/core/neighbour.c:1618
  NF_HOOK_COND include/linux/netfilter.h:307 [inline]
  ip6_output+0x340/0x550 net/ipv6/ip6_output.c:247
  NF_HOOK+0x9e/0x380 include/linux/netfilter.h:318
  mld_sendpack+0x8d4/0xe60 net/ipv6/mcast.c:1855
  mld_send_cr net/ipv6/mcast.c:2154 [inline]
  mld_ifc_work+0x83e/0xd60 net/ipv6/mcast.c:2693
  process_one_work kernel/workqueue.c:3257 [inline]
  process_scheduled_works+0xad1/0x1770 kernel/workqueue.c:3340
  worker_thread+0x8a0/0xda0 kernel/workqueue.c:3421
  kthread+0x711/0x8a0 kernel/kthread.c:463
  ret_from_fork+0x510/0xa50 arch/x86/kernel/process.c:158
  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246

## Affected

- `linux_kernel >= 3.10.1, < 5.10.249`
- `linux_kernel >= 5.11, < 5.15.199`
- `linux_kernel >= 5.16, < 6.1.162`
- `linux_kernel >= 6.2, < 6.6.122`
- `linux_kernel >= 6.7, < 6.12.67`
- `linux_kernel >= 6.13, < 6.18.7`
- `linux_kernel = 3.10`
- `linux_kernel = 6.19`

## Remediation

Upgrade past the affected range:

- `linux_kernel 6.18.7`