---
title: "CVE-2026-89563: Linux Kernel - Use After Free"
description: "Linux kernel ip6_tunnel contains a memory management flaw in ip6_tnl_xmit() caused by improper skb headroom expansion using skb_realloc_headroom(), letting kernel components potentially free stale skb pointers, exploit requires kernel-level interaction."
url: https://panop.io/threat-heartbeat/CVE-2026-89563/
---

# CVE-2026-89563 Linux Kernel - Use After Free

Linux kernel ip6\_tunnel contains a memory management flaw in ip6\_tnl\_xmit() caused by improper skb headroom expansion using skb\_realloc\_headroom(), letting kernel components potentially free stale skb pointers, exploit requires kernel-level interaction.

CVSS base score 7.8 /10

High

CISA KEV

Not listed

Public exploit

None known

Authentication

Required

EPSS

0.14% chance of exploitation in 30 days

[View the NVD record ↗](https://nvd.nist.gov/vuln/detail/CVE-2026-89563)

## Details

Type

Use After Free

Impact

Denial Of Service

CVSS vector

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Published

11 September 2026

Updated

15 October 2026

## Vendor fix

Update to the latest Linux kernel version containing the fix using skb\_cow\_head() in ip6\_tnl\_xmit().

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

## References

- [https://nvd.nist.gov/vuln/detail/CVE-2026-89563](https://nvd.nist.gov/vuln/detail/CVE-2026-89563)
- [https://git.kernel.org/stable/c/37df5bc6b5ccad88c2faa0f5466f150178882b74](https://git.kernel.org/stable/c/37df5bc6b5ccad88c2faa0f5466f150178882b74)
- [https://git.kernel.org/stable/c/87f21b59ddc618eff9670c174842964ad65fdade](https://git.kernel.org/stable/c/87f21b59ddc618eff9670c174842964ad65fdade)
- [https://git.kernel.org/stable/c/8fc56ca49fc0ee1725b55c67bb43ab0dd01f3f52](https://git.kernel.org/stable/c/8fc56ca49fc0ee1725b55c67bb43ab0dd01f3f52)
- [https://git.kernel.org/stable/c/b36dfd6e8cff00cea81c11cc0af88d1564763461](https://git.kernel.org/stable/c/b36dfd6e8cff00cea81c11cc0af88d1564763461)
- [https://git.kernel.org/stable/c/629d5557e635cdbc109a14ed913ba5a540e3f79a](https://git.kernel.org/stable/c/629d5557e635cdbc109a14ed913ba5a540e3f79a)
- [https://git.kernel.org/stable/c/6e8eff8ed13b14708bc39f170144eacde494aac6](https://git.kernel.org/stable/c/6e8eff8ed13b14708bc39f170144eacde494aac6)
- [https://git.kernel.org/stable/c/dc1a319a4815c074914e2812e0e9cd0164ca682b](https://git.kernel.org/stable/c/dc1a319a4815c074914e2812e0e9cd0164ca682b)
- [https://git.kernel.org/stable/c/defa0adeff132cc90ed66915b9a104d9393e1e54](https://git.kernel.org/stable/c/defa0adeff132cc90ed66915b9a104d9393e1e54)

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## What this record can't tell you

- Whether you run the affected software, and where
- Whether an attacker can actually reach and exploit it
- The misconfigurations that never get a CVE number
- What it would cost the business, ranked into what to fix first

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