---
title: "CVE-2026-89630: Linux Kernel smb client - Broken Access Control"
description: "Linux kernel smb client contains a broken access control vulnerability caused by incorrect data_offset bound check in is_valid_oplock_break(), letting attackers bypass read overflow protections, exploit requires crafted SMB messages."
url: https://panop.io/threat-heartbeat/CVE-2026-89630/
---

# CVE-2026-89630 Linux Kernel smb client - Broken Access Control

Linux kernel smb client contains a broken access control vulnerability caused by incorrect data\_offset bound check in is\_valid\_oplock\_break(), letting attackers bypass read overflow protections, exploit requires crafted SMB messages.

CVSS base score 9.1 /10

Critical

CISA KEV

Not listed

Public exploit

None known

Authentication

Not required

EPSS

0.54% chance of exploitation in 30 days

[View the NVD record ↗](https://nvd.nist.gov/vuln/detail/CVE-2026-89630)

## Details

Type

Broken Access Control

Impact

Denial Of Service

CVSS vector

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

Published

11 September 2026

Updated

15 October 2026

## Vendor fix

Update to the latest Linux kernel version containing the fix for is\_valid\_oplock\_break() data\_offset bound restoration.

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-2026-89630](https://nvd.nist.gov/vuln/detail/CVE-2026-89630)
- [https://git.kernel.org/stable/c/5b16a1967a01ad4496a7206a87c3eb16f1df2b05](https://git.kernel.org/stable/c/5b16a1967a01ad4496a7206a87c3eb16f1df2b05)
- [https://git.kernel.org/stable/c/ba22f575de9deeae4ae0859ca4315a7698226237](https://git.kernel.org/stable/c/ba22f575de9deeae4ae0859ca4315a7698226237)

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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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