---
title: "CVE-2026-89713: Linux Kernel NFSD - Race Condition"
description: "Linux kernel NFSD contains a time-of-check to time-of-use (TOCTOU) vulnerability caused by checking truncate permission without inode lock, letting attackers bypass append-only file restrictions during concurrent file size changes, exploit requires concurrent file append operations."
url: https://panop.io/threat-heartbeat/CVE-2026-89713/
---

# CVE-2026-89713 Linux Kernel NFSD - Race Condition

Linux kernel NFSD contains a time-of-check to time-of-use (TOCTOU) vulnerability caused by checking truncate permission without inode lock, letting attackers bypass append-only file restrictions during concurrent file size changes, exploit requires concurrent file append operations.

CVSS base score 9.1 /10

Critical

CISA KEV

Not listed

Public exploit

None known

EPSS

0.61% chance of exploitation in 30 days

[View the NVD record ↗](https://nvd.nist.gov/vuln/detail/CVE-2026-89713)

## Details

Type

Race Condition

Impact

Data Tampering

CVSS vector

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

Published

11 September 2026

Updated

15 October 2026

## Vendor fix

Update to the latest Linux kernel version with the NFSD inode lock fix.

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-2026-89713](https://nvd.nist.gov/vuln/detail/CVE-2026-89713)
- [https://git.kernel.org/stable/c/b778e0e0a16759f22a70579c3cf8d254a40d4a7f](https://git.kernel.org/stable/c/b778e0e0a16759f22a70579c3cf8d254a40d4a7f)
- [https://git.kernel.org/stable/c/d8352da196349182e1afd5a93308256cddc0a97d](https://git.kernel.org/stable/c/d8352da196349182e1afd5a93308256cddc0a97d)
- [https://git.kernel.org/stable/c/3afa17d93ba8c925f49370c816c6dae5112d8c24](https://git.kernel.org/stable/c/3afa17d93ba8c925f49370c816c6dae5112d8c24)
- [https://git.kernel.org/stable/c/44086254479035de42ca3d286ecf25521d4e6325](https://git.kernel.org/stable/c/44086254479035de42ca3d286ecf25521d4e6325)

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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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