---
title: "CVE-2026-89688: Linux Kernel - Use After Free"
description: "Linux kernel contains a use-after-free vulnerability caused by incorrect reference counting in nfsd4_cstate_assign_replay() during seqid_op replay retry, letting attackers cause memory corruption or denial of service, exploit requires attacker to trigger specific NFSv4 operations."
url: https://panop.io/threat-heartbeat/CVE-2026-89688/
---

# CVE-2026-89688 Linux Kernel - Use After Free

Linux kernel contains a use-after-free vulnerability caused by incorrect reference counting in nfsd4\_cstate\_assign\_replay() during seqid\_op replay retry, letting attackers cause memory corruption or denial of service, exploit requires attacker to trigger specific NFSv4 operations.

CVSS base score 9.8 /10

Critical

CISA KEV

Not listed

Public exploit

None known

Authentication

Not required

EPSS

0.74% chance of exploitation in 30 days

[View the NVD record ↗](https://nvd.nist.gov/vuln/detail/CVE-2026-89688)

## Details

Type

Use After Free

Impact

Use After Free, Denial Of Service

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 stateid reference handling.

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-2026-89688](https://nvd.nist.gov/vuln/detail/CVE-2026-89688)
- [https://git.kernel.org/stable/c/69ed78b6b947c9257213164678b4edf17533093b](https://git.kernel.org/stable/c/69ed78b6b947c9257213164678b4edf17533093b)
- [https://git.kernel.org/stable/c/f7cb90ddc021747fc9abfd4cf5252d425fd34eec](https://git.kernel.org/stable/c/f7cb90ddc021747fc9abfd4cf5252d425fd34eec)
- [https://git.kernel.org/stable/c/00843074d9b84824552c9679d423d29500ca5de0](https://git.kernel.org/stable/c/00843074d9b84824552c9679d423d29500ca5de0)
- [https://git.kernel.org/stable/c/5e4627d3513e60accfce9d5f4c7fa95251ef93d6](https://git.kernel.org/stable/c/5e4627d3513e60accfce9d5f4c7fa95251ef93d6)

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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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