---
id: CVE-2026-63993
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  vxlan: do not reuse cached ip_hdr() value after skb_tunnel_check_pmtu()

  skb_tunnel_check_pmtu() can change skb->head.

  Reusing old_iph afer skb_tunnel_check_pmtu() can…
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  vxlan: do not reuse cached ip_hdr() value after skb_tunnel_check_pmtu()

  skb_tunnel_check_pmtu() can change skb->head.

  Reusing old_iph afer skb_tunnel_check_pmtu() can…
severity: critical
cvss: 9.8
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H'
cwe:
  - CWE-416
vendor: linux
product: linux_kernel
affected:
  - 'linux_kernel >= 5.9, < 5.10.259'
  - 'linux_kernel >= 5.11, < 5.15.210'
  - 'linux_kernel >= 5.16, < 6.1.176'
  - 'linux_kernel >= 6.2, < 6.6.143'
  - 'linux_kernel >= 6.7, < 6.12.93'
  - 'linux_kernel >= 6.13, < 6.18.35'
  - 'linux_kernel >= 6.19, < 7.0.12'
  - linux_kernel = 7.1
patched:
  - linux_kernel 7.0.12
published: '2026-07-19'
updated: '2026-10-02'
sourceUpdated: '2026-10-02T19:57:14.137'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-63993'
references:
  - url: 'https://git.kernel.org/stable/c/5303925e360527243b46a440a04667826bbc72b7'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/609e63312c29aad18026a1d3222e123d4b6b0feb'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/6b8bfce9d2f774d2c2243e0248e03efb99bba6c0'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/7d9ef0cb271555d8cf39fefe6c981e1493b25ecf'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/8d435d68d71fb875876b722f4136caf74f2f48bd'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/9257f56ac47ef1976bcd056cf986a9988eeec67a'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/a493efd4336cf19122ae0e4cbb3d31b32d70deea'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/dc3bfa050f873371e745bdf478b1f5b738e5733d'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
tags:
  - nvd
epss: 0.00514
epssPercentile: 0.41687
ingestedAt: '2026-10-02T22:33:09.809Z'
---

## Overview

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

vxlan: do not reuse cached ip_hdr() value after skb_tunnel_check_pmtu()

skb_tunnel_check_pmtu() can change skb->head.

Reusing old_iph afer skb_tunnel_check_pmtu() can cause an UAF.

Use instead ip_hdr(skb) as done in drivers/net/bareudp.c
and drivers/net/geneve.c.

Found by Sashiko.

## Affected

- `linux_kernel >= 5.9, < 5.10.259`
- `linux_kernel >= 5.11, < 5.15.210`
- `linux_kernel >= 5.16, < 6.1.176`
- `linux_kernel >= 6.2, < 6.6.143`
- `linux_kernel >= 6.7, < 6.12.93`
- `linux_kernel >= 6.13, < 6.18.35`
- `linux_kernel >= 6.19, < 7.0.12`
- `linux_kernel = 7.1`

## Remediation

Upgrade past the affected range:

- `linux_kernel 7.0.12`