---
title: "CVE-2026-89659: Linux Kernel - Use After Free"
description: "Linux kernel contains a use-after-free vulnerability in NFSD delegation revoke caused by improper client reference handling in nfs4_laundromat, letting attackers cause memory corruption, exploit requires client delegation timeout."
url: https://panop.io/threat-heartbeat/CVE-2026-89659/
---

# CVE-2026-89659 Linux Kernel - Use After Free

Linux kernel contains a use-after-free vulnerability in NFSD delegation revoke caused by improper client reference handling in nfs4\_laundromat, letting attackers cause memory corruption, exploit requires client delegation timeout.

CVSS base score 9.8 /10

Critical

CISA KEV

Not listed

Public exploit

None known

Authentication

Not required

EPSS

0.44% chance of exploitation in 30 days

[View the NVD record ↗](https://nvd.nist.gov/vuln/detail/CVE-2026-89659)

## Details

Type

Use After Free

Impact

Denial Of Service, Remote Code Execution

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/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 for NFSD delegation revoke use-after-free.

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-2026-89659](https://nvd.nist.gov/vuln/detail/CVE-2026-89659)
- [https://git.kernel.org/stable/c/2a9d637c2a8fd8ac29ad9b29f28d122ef75c1a56](https://git.kernel.org/stable/c/2a9d637c2a8fd8ac29ad9b29f28d122ef75c1a56)
- [https://git.kernel.org/stable/c/3c0a53ee0b442348d8d2286d6960d3f07bb3a3d3](https://git.kernel.org/stable/c/3c0a53ee0b442348d8d2286d6960d3f07bb3a3d3)
- [https://git.kernel.org/stable/c/4683ca76b3b7e5808338491c6eb3c20e6b4894d5](https://git.kernel.org/stable/c/4683ca76b3b7e5808338491c6eb3c20e6b4894d5)
- [https://git.kernel.org/stable/c/0dd276b1324a5e08e83c6f675919946c9f0d61c9](https://git.kernel.org/stable/c/0dd276b1324a5e08e83c6f675919946c9f0d61c9)

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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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