---
id: CVE-2026-97964
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  ppp_synctty: ensure a writeable skb header

  ppp_sync_txmunge() checks headroom before prepending the address and
  control bytes, but does not ensure that the skb header …
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  ppp_synctty: ensure a writeable skb header

  ppp_sync_txmunge() checks headroom before prepending the address and
  control bytes, but does not ensure that the skb header …
severity: medium
cvss: 5.5
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'
cwe:
  - CWE-787
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 4cf476ced45d7f12df30a68e833b263e7a2202d1 <
    25e03eeead2c49748c7582dfb64c205f93a42d00
  - >-
    Linux >= 4cf476ced45d7f12df30a68e833b263e7a2202d1 <
    a256f9925288ef47de8febed5c38d5cc21340211
  - >-
    Linux >= 4cf476ced45d7f12df30a68e833b263e7a2202d1 <
    7953946f68262a8bb137aa101249adef6e029652
  - >-
    Linux >= 4cf476ced45d7f12df30a68e833b263e7a2202d1 <
    3af7797fbabc84992e0ca5ad2bc0ca8537d053ef
  - >-
    Linux >= 4cf476ced45d7f12df30a68e833b263e7a2202d1 <
    0996c3e6bcc6ae08cb371ed43648c9f7f748ae6e
  - >-
    Linux >= 4cf476ced45d7f12df30a68e833b263e7a2202d1 <
    15d0a6c9a42df2d745c37510dba828f6dbe60d9f
  - >-
    Linux >= 4cf476ced45d7f12df30a68e833b263e7a2202d1 <
    8aaeb56aff2a557a88f83ae866da2c91ad247e59
  - Linux 5.11
published: '2026-09-25'
updated: '2026-10-03'
sourceUpdated: '2026-10-03T11:18:21.377'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-97964'
references:
  - url: 'https://git.kernel.org/stable/c/0996c3e6bcc6ae08cb371ed43648c9f7f748ae6e'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/15d0a6c9a42df2d745c37510dba828f6dbe60d9f'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/25e03eeead2c49748c7582dfb64c205f93a42d00'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/3af7797fbabc84992e0ca5ad2bc0ca8537d053ef'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/7953946f68262a8bb137aa101249adef6e029652'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/8aaeb56aff2a557a88f83ae866da2c91ad247e59'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/a256f9925288ef47de8febed5c38d5cc21340211'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-97964.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-97964'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2541113'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-97964'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-97964'
  - url: >-
      https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-97964.mbox
tags:
  - nvd
  - cve.org
  - csaf
  - vex
  - red-hat
epss: 0.00173
epssPercentile: 0.06628
cvssSource: vendor
ingestedAt: '2026-09-25T11:06:38.874Z'
---

## Overview

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

ppp_synctty: ensure a writeable skb header

ppp_sync_txmunge() checks headroom before prepending the address and
control bytes, but does not ensure that the skb header is writable.
A received skb can reach this function through PPP channel bridging
without passing through ppp_start_xmit(), which calls skb_cow_head().

For example, a PPPoE frame may share its buffer with a clone queued to
an AF_PACKET socket. If it is bridged to a synchronous tty channel, the
address/control bytes can overwrite data still visible to that socket.

Use skb_cow_head() to ensure both sufficient headroom and a writable
header.

## Remediation

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

## Vendor advisories

- **Red Hat VEX** · Moderate · affected: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 9, Red Hat OpenShift Container Platform 4 · no fix planned: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 9, Red Hat OpenShift Container Platform 4 · updated 2026-10-17 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-97964.json)