---
title: "CVE-2026-89631: Linux kernel smb client - Out of Bounds Read"
description: "Linux kernel smb client contains a buffer overflow caused by improper bounds checking of tree connect response byte count in CIFSTCon(), letting attackers cause memory corruption, exploit requires crafted server response."
url: https://panop.io/threat-heartbeat/CVE-2026-89631/
---

# CVE-2026-89631 Linux kernel smb client - Out of Bounds Read

Linux kernel smb client contains a buffer overflow caused by improper bounds checking of tree connect response byte count in CIFSTCon(), letting attackers cause memory corruption, exploit requires crafted server response.

CVSS base score 9.1 /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-2026-89631)

## Details

Type

Out of Bounds Read

Impact

Information Disclosure, 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.

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-2026-89631](https://nvd.nist.gov/vuln/detail/CVE-2026-89631)
- [https://git.kernel.org/stable/c/3be89e8039a85fa3b6cd5f9dcc4c1459eb356c2d](https://git.kernel.org/stable/c/3be89e8039a85fa3b6cd5f9dcc4c1459eb356c2d)
- [https://git.kernel.org/stable/c/411e484fe71a7f1028de617447edad9cb6d9d68a](https://git.kernel.org/stable/c/411e484fe71a7f1028de617447edad9cb6d9d68a)
- [https://git.kernel.org/stable/c/65deb18359341141d37dc86fc7853511be3c87a7](https://git.kernel.org/stable/c/65deb18359341141d37dc86fc7853511be3c87a7)

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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

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

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