---
id: CVE-2026-80731
title: 'net: remove CAP_SYS_RAWIO zero-padding in dev_validate_header'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  net: remove CAP_SYS_RAWIO zero-padding in dev_validate_header

  dev_validate_header() reads dev->hard_header_len directly when
  zero-padding short link layer headers for …
severity: high
cvss: 7.8
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'
cvssSource: cna
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= b5518429e70cd783b8ca52335456172c1a0589f6 <
    53fd7f912c0877647d6a1e1877f5ea8535ee0b4a
  - >-
    Linux >= 2793a23aacbd754dbbb5cb75093deb7e4103bace <
    fa6d98dd925e72fc028b26a0cbbff9d2f0601ff6
  - >-
    Linux >= 2793a23aacbd754dbbb5cb75093deb7e4103bace <
    8fc9816404166a90ed8d544dc52482fafffb6d9f
  - >-
    Linux >= 2793a23aacbd754dbbb5cb75093deb7e4103bace <
    b0f92a5731dc82556a9ae005cc35f71ab136307b
  - >-
    Linux >= 2793a23aacbd754dbbb5cb75093deb7e4103bace <
    99df6b7a713f96eda206680d100b76e15f9d9b69
  - >-
    Linux >= 2793a23aacbd754dbbb5cb75093deb7e4103bace <
    74e035f07f53feca09e2352e77fccb09cad5e208
  - >-
    Linux >= 2793a23aacbd754dbbb5cb75093deb7e4103bace <
    dbb30dc943a93e083f1e531bfdc6779e57de40d0
  - >-
    Linux >= 2793a23aacbd754dbbb5cb75093deb7e4103bace <
    fc902f52a02298c7432b2334c0c82a2885a1a8b6
  - >-
    Linux >= 2793a23aacbd754dbbb5cb75093deb7e4103bace <
    3b9a324e646d3657a8d9806dfbfe4f3e4066e882
  - Linux f58a6c08ebdfa978178bbca78c2ba744a2665912
  - Linux 1df16498dfd0d5a129bdf2982d9a08df73e8923d
  - Linux 8b8d278aa4de9335682bbd4a3bb619af015c859e
  - Linux 6804052fa9d86e9a512c88b24a5debbfc1a490fc
  - Linux >= 3.2.80 < 3.2.81
  - Linux >= 3.16.36 < 3.17
  - Linux >= 4.1.28 < 4.2
  - Linux >= 4.4.8 < 4.5
  - Linux >= 4.5.2 < 4.6
  - Linux 4.6
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: total
  timestamp: '2026-10-16T19:21:14.341917Z'
published: '2026-09-03'
updated: '2026-10-16'
sourceUpdated: '2026-10-16T19:26:36.020Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-80731'
references:
  - url: 'https://git.kernel.org/stable/c/53fd7f912c0877647d6a1e1877f5ea8535ee0b4a'
  - url: 'https://git.kernel.org/stable/c/fa6d98dd925e72fc028b26a0cbbff9d2f0601ff6'
  - url: 'https://git.kernel.org/stable/c/8fc9816404166a90ed8d544dc52482fafffb6d9f'
  - url: 'https://git.kernel.org/stable/c/b0f92a5731dc82556a9ae005cc35f71ab136307b'
  - url: 'https://git.kernel.org/stable/c/99df6b7a713f96eda206680d100b76e15f9d9b69'
  - url: 'https://git.kernel.org/stable/c/74e035f07f53feca09e2352e77fccb09cad5e208'
  - url: 'https://git.kernel.org/stable/c/dbb30dc943a93e083f1e531bfdc6779e57de40d0'
  - url: 'https://git.kernel.org/stable/c/fc902f52a02298c7432b2334c0c82a2885a1a8b6'
  - url: 'https://git.kernel.org/stable/c/3b9a324e646d3657a8d9806dfbfe4f3e4066e882'
tags:
  - cve.org
epss: 0.00142
epssPercentile: 0.03105
ingestedAt: '2026-10-16T19:46:24.301Z'
---

## Overview

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

net: remove CAP_SYS_RAWIO zero-padding in dev_validate_header

dev_validate_header() reads dev->hard_header_len directly when
zero-padding short link layer headers for CAP_SYS_RAWIO holders:

    if (capable(CAP_SYS_RAWIO)) {
        memset(ll_header + len, 0, dev->hard_header_len - len);
        return true;
    }

Packet send paths call dev_validate_header() on skbs whose headroom was
allocated from an earlier hard_header_len read. If the device is
reconfigured so that dev->hard_header_len increases before validation,
the memset writes past the reserved buffer, an out-of-bounds write.

This out-of-bounds write is masked in some SOCK_RAW paths today because
the same concurrent increase can first make skb_push() exceed the
reserved headroom and trigger skb_under_panic(). Remove the zero-padding
branch before making those hard_header_len reads consistent, so the
snapshot fixes do not turn a loud panic into a silent overwrite.

This path is only reached for variable length L2 protocols, where
len < hard_header_len but len >= min_header_len. No remaining in-tree
variable length L2 protocol implements header_ops->validate, and the
CAP_SYS_RAWIO bypass that zero-pads and accepts short headers has no
real value beyond allowing testing of intentionally malformed input.

Drop the CAP_SYS_RAWIO branch. The remaining reads of
dev->hard_header_len in dev_validate_header() are comparisons only and
have no memory safety impact.

## Affected

- `Linux >= b5518429e70cd783b8ca52335456172c1a0589f6 < 53fd7f912c0877647d6a1e1877f5ea8535ee0b4a`
- `Linux >= 2793a23aacbd754dbbb5cb75093deb7e4103bace < fa6d98dd925e72fc028b26a0cbbff9d2f0601ff6`
- `Linux >= 2793a23aacbd754dbbb5cb75093deb7e4103bace < 8fc9816404166a90ed8d544dc52482fafffb6d9f`
- `Linux >= 2793a23aacbd754dbbb5cb75093deb7e4103bace < b0f92a5731dc82556a9ae005cc35f71ab136307b`
- `Linux >= 2793a23aacbd754dbbb5cb75093deb7e4103bace < 99df6b7a713f96eda206680d100b76e15f9d9b69`
- `Linux >= 2793a23aacbd754dbbb5cb75093deb7e4103bace < 74e035f07f53feca09e2352e77fccb09cad5e208`
- `Linux >= 2793a23aacbd754dbbb5cb75093deb7e4103bace < dbb30dc943a93e083f1e531bfdc6779e57de40d0`
- `Linux >= 2793a23aacbd754dbbb5cb75093deb7e4103bace < fc902f52a02298c7432b2334c0c82a2885a1a8b6`
- `Linux >= 2793a23aacbd754dbbb5cb75093deb7e4103bace < 3b9a324e646d3657a8d9806dfbfe4f3e4066e882`
- `Linux f58a6c08ebdfa978178bbca78c2ba744a2665912`
- `Linux 1df16498dfd0d5a129bdf2982d9a08df73e8923d`
- `Linux 8b8d278aa4de9335682bbd4a3bb619af015c859e`
- `Linux 6804052fa9d86e9a512c88b24a5debbfc1a490fc`
- `Linux >= 3.2.80 < 3.2.81`
- `Linux >= 3.16.36 < 3.17`
- `Linux >= 4.1.28 < 4.2`
- `Linux >= 4.4.8 < 4.5`
- `Linux >= 4.5.2 < 4.6`
- `Linux 4.6`

## Remediation

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