---
id: CVE-2026-23095
title: 'gue: Fix skb memleak with inner IP protocol 0.'
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'
cvssSource: cna
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 37dd0247797b168ad1cc7f5dbec825a1ee66535b <
    886f186328b718400dbf79e1bc8cbcbd710ab766
  - >-
    Linux >= 37dd0247797b168ad1cc7f5dbec825a1ee66535b <
    380a82d36e37db49fd41ecc378c22fd29392e96a
  - >-
    Linux >= 37dd0247797b168ad1cc7f5dbec825a1ee66535b <
    536f5bbc322eb1e175bdd1ced22b236a951c4d8f
  - >-
    Linux >= 37dd0247797b168ad1cc7f5dbec825a1ee66535b <
    f87b9b7a618c82e7465e872eb10e14c803871892
  - >-
    Linux >= 37dd0247797b168ad1cc7f5dbec825a1ee66535b <
    ce569b389a5c78d64788a5ea94560e17fa574b35
  - >-
    Linux >= 37dd0247797b168ad1cc7f5dbec825a1ee66535b <
    5437a279804ced8088cabb945dba88a26d828f8c
  - >-
    Linux >= 37dd0247797b168ad1cc7f5dbec825a1ee66535b <
    9a56796ad258786d3624eef5aefba394fc9bdded
  - Linux 3.18
ssvc:
  exploitation: none
  automatable: 'yes'
  technicalImpact: partial
  timestamp: '2026-06-16T20:19:57.582925Z'
published: '2026-02-04'
updated: '2026-09-08'
sourceUpdated: '2026-09-08T08:44:52.392Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-23095'
references:
  - url: 'https://git.kernel.org/stable/c/886f186328b718400dbf79e1bc8cbcbd710ab766'
  - url: 'https://git.kernel.org/stable/c/380a82d36e37db49fd41ecc378c22fd29392e96a'
  - url: 'https://git.kernel.org/stable/c/536f5bbc322eb1e175bdd1ced22b236a951c4d8f'
  - url: 'https://git.kernel.org/stable/c/f87b9b7a618c82e7465e872eb10e14c803871892'
  - url: 'https://git.kernel.org/stable/c/ce569b389a5c78d64788a5ea94560e17fa574b35'
  - url: 'https://git.kernel.org/stable/c/5437a279804ced8088cabb945dba88a26d828f8c'
  - url: 'https://git.kernel.org/stable/c/9a56796ad258786d3624eef5aefba394fc9bdded'
tags:
  - cve.org
epss: 0.00253
epssPercentile: 0.15152
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 >= 37dd0247797b168ad1cc7f5dbec825a1ee66535b < 886f186328b718400dbf79e1bc8cbcbd710ab766`
- `Linux >= 37dd0247797b168ad1cc7f5dbec825a1ee66535b < 380a82d36e37db49fd41ecc378c22fd29392e96a`
- `Linux >= 37dd0247797b168ad1cc7f5dbec825a1ee66535b < 536f5bbc322eb1e175bdd1ced22b236a951c4d8f`
- `Linux >= 37dd0247797b168ad1cc7f5dbec825a1ee66535b < f87b9b7a618c82e7465e872eb10e14c803871892`
- `Linux >= 37dd0247797b168ad1cc7f5dbec825a1ee66535b < ce569b389a5c78d64788a5ea94560e17fa574b35`
- `Linux >= 37dd0247797b168ad1cc7f5dbec825a1ee66535b < 5437a279804ced8088cabb945dba88a26d828f8c`
- `Linux >= 37dd0247797b168ad1cc7f5dbec825a1ee66535b < 9a56796ad258786d3624eef5aefba394fc9bdded`
- `Linux 3.18`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.