---
title: "CVE-2026-90009: Linux Kernel - Time-of-Check to Time-of-Use (TOCTOU)"
description: "Linux kernel contains a time-of-check to time-of-use (TOCTOU) vulnerability in scsi bsg io_uring passthrough command setup caused by unsynchronized access to shared mmap'd SQE fields, letting attackers cause buffer overflow, exploit requires userspace to modify shared memory after validation."
url: https://panop.io/threat-heartbeat/CVE-2026-90009/
---

# CVE-2026-90009 Linux Kernel - Time-of-Check to Time-of-Use (TOCTOU)

Linux kernel contains a time-of-check to time-of-use (TOCTOU) vulnerability in scsi bsg io\_uring passthrough command setup caused by unsynchronized access to shared mmap'd SQE fields, letting attackers cause buffer overflow, exploit requires userspace to modify shared memory after validation.

CVSS base score 7.8 /10

High

CISA KEV

Not listed

Public exploit

None known

EPSS

0.17% chance of exploitation in 30 days

[View the NVD record ↗](https://nvd.nist.gov/vuln/detail/CVE-2026-90009)

## Details

Type

Time-of-Check to Time-of-Use (TOCTOU)

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

16 September 2026

Updated

15 October 2026

## Vendor fix

Update to the latest Linux kernel version with the TOCTOU fix applied.

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-2026-90009](https://nvd.nist.gov/vuln/detail/CVE-2026-90009)
- [https://git.kernel.org/stable/c/4b3c5965fca99f62d31c963294bd5b23cc488e97](https://git.kernel.org/stable/c/4b3c5965fca99f62d31c963294bd5b23cc488e97)
- [https://git.kernel.org/stable/c/f033530105aa73d82c121d54b57f358e4865d2f4](https://git.kernel.org/stable/c/f033530105aa73d82c121d54b57f358e4865d2f4)

[← All CVEs](https://panop.io/threat-heartbeat/)

## 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

Panop answers these inside your environment, for this CVE and every other finding.

[Book a demo](https://panop.io/demo)