---
id: CVE-2026-90160
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  lwt_bpf: Restore reserved headroom after xmit program

  ip_finish_output2() expands an skb to LL_RESERVED_SPACE(dev) before LWT
  xmit
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  lwt_bpf: Restore reserved headroom after xmit program

  ip_finish_output2() expands an skb to LL_RESERVED_SPACE(dev) before LWT
  xmit. An LWT_XMIT BPF program can then mo…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 3a0af8fd61f90920f6fa04e4f1e9a6a73c1b4fd2 <
    753e5cdcca5474d230d62bb3489e5168ab27c272
  - >-
    Linux >= 3a0af8fd61f90920f6fa04e4f1e9a6a73c1b4fd2 <
    c488071c3441fa34f5a87cd6c12ce2cc6304f20e
  - >-
    Linux >= 3a0af8fd61f90920f6fa04e4f1e9a6a73c1b4fd2 <
    a38c0eb447e2dd0120a2ebcdba470f9505ac8907
  - >-
    Linux >= 3a0af8fd61f90920f6fa04e4f1e9a6a73c1b4fd2 <
    de2b2004e16f2930eb689175e2c1998b0a68d499
  - >-
    Linux >= 3a0af8fd61f90920f6fa04e4f1e9a6a73c1b4fd2 <
    7d043e24520a273c362be5dd7d9c82796879a49b
  - >-
    Linux >= 3a0af8fd61f90920f6fa04e4f1e9a6a73c1b4fd2 <
    7cf561843ed0ad57501892a65abb77957e6c800f
  - >-
    Linux >= 3a0af8fd61f90920f6fa04e4f1e9a6a73c1b4fd2 <
    179a5b2171573d94a25c9aa8e1c9f9ac352ad316
  - >-
    Linux >= 3a0af8fd61f90920f6fa04e4f1e9a6a73c1b4fd2 <
    5fe7007aed9ad069b2bd77e5d0c875c64f5c0269
  - Linux 4.10
published: '2026-09-17'
updated: '2026-09-17'
sourceUpdated: '2026-09-17T17:17:09.190'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-90160'
references:
  - url: 'https://git.kernel.org/stable/c/179a5b2171573d94a25c9aa8e1c9f9ac352ad316'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/5fe7007aed9ad069b2bd77e5d0c875c64f5c0269'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/753e5cdcca5474d230d62bb3489e5168ab27c272'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/7cf561843ed0ad57501892a65abb77957e6c800f'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/7d043e24520a273c362be5dd7d9c82796879a49b'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/a38c0eb447e2dd0120a2ebcdba470f9505ac8907'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/c488071c3441fa34f5a87cd6c12ce2cc6304f20e'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/de2b2004e16f2930eb689175e2c1998b0a68d499'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
tags:
  - nvd
  - cve.org
ingestedAt: '2026-09-17T16:21:47.872Z'
epss: 0.00216
epssPercentile: 0.12008
---

## Overview

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

lwt_bpf: Restore reserved headroom after xmit program

ip_finish_output2() expands an skb to LL_RESERVED_SPACE(dev) before LWT
xmit. An LWT_XMIT BPF program can then modify the skb head and still
return BPF_OK, so bpf_xmit() rechecks the remaining headroom before the
skb continues to neighbour output.

That recheck uses dst->dev->hard_header_len. This is not enough for the
neighbour cached-header path: neigh_hh_output() copies the cached hardware
header using the aligned hh_cache size, HH_DATA_MOD for short headers or
HH_DATA_ALIGN(hh_len) otherwise.

On Ethernet, hard_header_len is 14 but the cached copy needs 16 bytes. If
an LWT_XMIT BPF program calls bpf_skb_change_head(skb, 1, 0), the skb can
still have 15 bytes of headroom after the program. The existing check
accepts that, after which neigh_hh_output() hits its headroom warning and
drops the skb.

Use LL_RESERVED_SPACE(dst->dev) in the post-BPF headroom check to match
the reservation made before LWT xmit.

## Remediation

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