---
id: CVE-2026-74310
title: 'vhost/net: complete zerocopy ubufs only once'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  vhost/net: complete zerocopy ubufs only once

  vhost-net initializes one ubuf_info per outstanding zerocopy TX
  descriptor and hands it to the backend socket.  The networ…
severity: critical
cvss: 9.3
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H'
cvssSource: cna
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= bab632d69ee48a106e779b60cc01adfe80a72807 <
    ea71f873423fb73e66ad88936d6759ac0ad4aa53
  - >-
    Linux >= bab632d69ee48a106e779b60cc01adfe80a72807 <
    6445b945024f4c7675ae5352b2d5885cb1deea71
  - >-
    Linux >= bab632d69ee48a106e779b60cc01adfe80a72807 <
    a9f8a1d2e3ff511eafd4c5462481950c2f4d2b5d
  - >-
    Linux >= bab632d69ee48a106e779b60cc01adfe80a72807 <
    321c73baf54d971ce3771fea275c98a247f7ee35
  - >-
    Linux >= bab632d69ee48a106e779b60cc01adfe80a72807 <
    c069437924663539a93a1e5afe90838d9ccee284
  - >-
    Linux >= bab632d69ee48a106e779b60cc01adfe80a72807 <
    8f6898fe80794f2d7c3d38c1158c806e4074a1c4
  - Linux 3.1
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: total
  timestamp: '2026-10-16T18:52:56.702664Z'
published: '2026-08-15'
updated: '2026-10-16'
sourceUpdated: '2026-10-16T18:55:32.036Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-74310'
references:
  - url: 'https://git.kernel.org/stable/c/ea71f873423fb73e66ad88936d6759ac0ad4aa53'
  - url: 'https://git.kernel.org/stable/c/6445b945024f4c7675ae5352b2d5885cb1deea71'
  - url: 'https://git.kernel.org/stable/c/a9f8a1d2e3ff511eafd4c5462481950c2f4d2b5d'
  - url: 'https://git.kernel.org/stable/c/321c73baf54d971ce3771fea275c98a247f7ee35'
  - url: 'https://git.kernel.org/stable/c/c069437924663539a93a1e5afe90838d9ccee284'
  - url: 'https://git.kernel.org/stable/c/8f6898fe80794f2d7c3d38c1158c806e4074a1c4'
tags:
  - cve.org
epss: 0.0019
epssPercentile: 0.08112
ingestedAt: '2026-10-16T19:46:24.381Z'
---

## Overview

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

vhost/net: complete zerocopy ubufs only once

vhost-net initializes one ubuf_info per outstanding zerocopy TX
descriptor and hands it to the backend socket.  The networking stack may
then clone a zerocopy skb before all skb references are released.  For
example, batman-adv fragmentation reaches skb_split(), which calls
skb_zerocopy_clone() and increments the same ubuf_info refcount.

vhost_zerocopy_complete() currently treats every ubuf callback as a
completed vhost descriptor.  It dereferences ubuf->ctx, writes the
descriptor completion state, and drops the vhost_net_ubuf_ref even when
the callback only releases a cloned skb reference.  A backend reset can
therefore wait for and free the vhost_net_ubuf_ref while another cloned
skb still carries the same ubuf_info.  A later completion then
dereferences the freed ubufs pointer.

KASAN reports the stale completion as:

  BUG: KASAN: slab-use-after-free in vhost_zerocopy_complete+0x1d7/0x1f0
  BUG: KASAN: slab-use-after-free in vhost_zerocopy_complete+0x101/0x1f0
  vhost_zerocopy_complete
  skb_copy_ubufs
  __dev_forward_skb2
  veth_xmit

The freed object was allocated from vhost_net_ioctl() while setting the
backend and freed through kfree_rcu()/kvfree_rcu_bulk after backend
removal, while delayed skb completion still reached
vhost_zerocopy_complete().

Honor the generic ubuf_info refcount before touching vhost state, and run
the vhost descriptor completion only for the final ubuf reference.  This
matches the msg_zerocopy_complete() ownership rule for cloned zerocopy
skbs.

## Affected

- `Linux >= bab632d69ee48a106e779b60cc01adfe80a72807 < ea71f873423fb73e66ad88936d6759ac0ad4aa53`
- `Linux >= bab632d69ee48a106e779b60cc01adfe80a72807 < 6445b945024f4c7675ae5352b2d5885cb1deea71`
- `Linux >= bab632d69ee48a106e779b60cc01adfe80a72807 < a9f8a1d2e3ff511eafd4c5462481950c2f4d2b5d`
- `Linux >= bab632d69ee48a106e779b60cc01adfe80a72807 < 321c73baf54d971ce3771fea275c98a247f7ee35`
- `Linux >= bab632d69ee48a106e779b60cc01adfe80a72807 < c069437924663539a93a1e5afe90838d9ccee284`
- `Linux >= bab632d69ee48a106e779b60cc01adfe80a72807 < 8f6898fe80794f2d7c3d38c1158c806e4074a1c4`
- `Linux 3.1`

## Remediation

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