---
id: CVE-2026-23095
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  gue: Fix skb memleak with inner IP protocol 0.

  syzbot reported skb memleak below
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  gue: Fix skb memleak with inner IP protocol 0.

  syzbot reported skb memleak below. [0]

  The repro generated a GUE packet with its inner protocol 0.

  gue_udp_recv() retu…
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'
cwe:
  - CWE-401
vendor: linux
product: linux_kernel
affected:
  - 'linux_kernel >= 3.18, < 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, < 6.12.68'
  - 'linux_kernel >= 6.13, < 6.18.8'
  - linux_kernel = 6.19
patched:
  - linux_kernel 6.18.8
published: '2026-02-04'
updated: '2026-10-15'
sourceUpdated: '2026-10-15T02:18:41.837'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-23095'
references:
  - url: 'https://git.kernel.org/stable/c/380a82d36e37db49fd41ecc378c22fd29392e96a'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/536f5bbc322eb1e175bdd1ced22b236a951c4d8f'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/5437a279804ced8088cabb945dba88a26d828f8c'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/886f186328b718400dbf79e1bc8cbcbd710ab766'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/9a56796ad258786d3624eef5aefba394fc9bdded'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/ce569b389a5c78d64788a5ea94560e17fa574b35'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/f87b9b7a618c82e7465e872eb10e14c803871892'
    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: 0.00299
epssPercentile: 0.22409
ssvc:
  exploitation: none
  automatable: 'yes'
  technicalImpact: partial
  timestamp: '2026-06-16T20:19:57.582925Z'
ingestedAt: '2026-09-08T15:33:26.993Z'
---

## Overview

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

gue: Fix skb memleak with inner IP protocol 0.

syzbot reported skb memleak below. [0]

The repro generated a GUE packet with its inner protocol 0.

gue_udp_recv() returns -guehdr->proto_ctype for "resubmit"
in ip_protocol_deliver_rcu(), but this only works with
non-zero protocol number.

Let's drop such packets.

Note that 0 is a valid number (IPv6 Hop-by-Hop Option).

I think it is not practical to encap HOPOPT in GUE, so once
someone starts to complain, we could pass down a resubmit
flag pointer to distinguish two zeros from the upper layer:

  * no error
  * resubmit HOPOPT

[0]
BUG: memory leak
unreferenced object 0xffff888109695a00 (size 240):
  comm "syz.0.17", pid 6088, jiffies 4294943096
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    00 40 c2 10 81 88 ff ff 00 00 00 00 00 00 00 00  .@..............
  backtrace (crc a84b336f):
    kmemleak_alloc_recursive include/linux/kmemleak.h:44 [inline]
    slab_post_alloc_hook mm/slub.c:4958 [inline]
    slab_alloc_node mm/slub.c:5263 [inline]
    kmem_cache_alloc_noprof+0x3b4/0x590 mm/slub.c:5270
    __build_skb+0x23/0x60 net/core/skbuff.c:474
    build_skb+0x20/0x190 net/core/skbuff.c:490
    __tun_build_skb drivers/net/tun.c:1541 [inline]
    tun_build_skb+0x4a1/0xa40 drivers/net/tun.c:1636
    tun_get_user+0xc12/0x2030 drivers/net/tun.c:1770
    tun_chr_write_iter+0x71/0x120 drivers/net/tun.c:1999
    new_sync_write fs/read_write.c:593 [inline]
    vfs_write+0x45d/0x710 fs/read_write.c:686
    ksys_write+0xa7/0x170 fs/read_write.c:738
    do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
    do_syscall_64+0xa4/0xf80 arch/x86/entry/syscall_64.c:94
    entry_SYSCALL_64_after_hwframe+0x77/0x7f

## Affected

- `linux_kernel >= 3.18, < 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, < 6.12.68`
- `linux_kernel >= 6.13, < 6.18.8`
- `linux_kernel = 6.19`

## Remediation

Upgrade past the affected range:

- `linux_kernel 6.18.8`