---
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
  - CWE-825
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
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-63993.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-63993'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2502369'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-63993'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-63993'
  - url: >-
      https://lore.kernel.org/linux-cve-announce/2026071905-CVE-2026-63993-165e@gregkh/T
  - url: 'https://access.redhat.com/errata/RHSA-2026:83707'
  - url: 'https://access.redhat.com/errata/RHSA-2026:64775'
  - url: 'https://access.redhat.com/errata/RHSA-2026:76739'
tags:
  - nvd
  - cve.org
  - csaf
  - vex
  - red-hat
  - score-dispute
epss: 0.00514
epssPercentile: 0.43608
ingestedAt: '2026-10-02T22:33:09.809Z'
ssvc:
  exploitation: none
  automatable: 'yes'
  technicalImpact: total
  timestamp: '2026-10-16T15:34:49.188699Z'
scores:
  nvd: 9.8
  vendor: 7
  cna: 9.8
---

## 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`

## Vendor advisories

- **RHSA-2026:83707** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream EUS (v. 10.0), Red Hat Enterprise Linux BaseOS EUS (v. 10.0), Red Hat Enterprise Linux CodeReady Linux Builder EUS (v. 10.0), Red Hat Enterprise Linux Real Time for NFV EUS (v. 10.0), Red Hat Enterprise Linux Real Time EUS (v. 10.0) · released 2026-10-16 · [advisory](https://access.redhat.com/errata/RHSA-2026:83707)
- **RHSA-2026:64775** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream (v. 10), Red Hat Enterprise Linux BaseOS (v. 10), Red Hat Enterprise Linux CodeReady Linux Builder (v. 10), Red Hat Enterprise Linux Real Time for NFV (v. 10), Red Hat Enterprise Linux Real Time (v. 10) · released 2026-09-08 · [advisory](https://access.redhat.com/errata/RHSA-2026:64775)
- **RHSA-2026:76739** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream (v. 9), Red Hat Enterprise Linux BaseOS (v. 9), Red Hat Enterprise Linux CodeReady Linux Builder (v. 9), Red Hat Enterprise Linux Real Time for NFV (v. 9), Red Hat Enterprise Linux Real Time (v. 9) · released 2026-10-08 · [advisory](https://access.redhat.com/errata/RHSA-2026:76739)
- **Red Hat VEX** · Important · affected: Red Hat Enterprise Linux 9 · no fix planned: Red Hat Enterprise Linux 9 · updated 2026-10-16 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-63993.json)