---
id: CVE-2026-89631
title: >-
  kernel: smb: client: reject a tree connect response whose byte count is too
  small (CVE-2026-89631)
summary: >-
  A flaw was found in the Linux kernel's Server Message Block (SMB) client. A
  remote malicious SMB server could send a specially crafted tree connect
  response with a byte count that is too small. This incorrect handling can lead
  to an intege…
severity: high
cvss: 7
cvssVector: 'CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H'
cvssSource: vendor
cwe: CWE-125
vendor: Red Hat
product: Red Hat Enterprise Linux 9
affected:
  - enterprise_linux 10
  - enterprise_linux 8
  - enterprise_linux 9
  - openshift_container_platform 4
published: '2026-09-11'
updated: '2026-09-18'
sourceUpdated: '2026-09-18T22:33:58+00:00'
source: CSAF
sourceUrl: 'https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89631.json'
references:
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89631.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-89631'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2532089'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-89631'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-89631'
  - url: >-
      https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-89631.mbox
  - url: 'https://git.kernel.org/stable/c/3be89e8039a85fa3b6cd5f9dcc4c1459eb356c2d'
  - url: 'https://git.kernel.org/stable/c/411e484fe71a7f1028de617447edad9cb6d9d68a'
  - url: 'https://git.kernel.org/stable/c/65deb18359341141d37dc86fc7853511be3c87a7'
tags:
  - csaf
  - vex
  - red-hat
  - cve.org
  - score-dispute
epss: 0.00632
epssPercentile: 0.48028
scores:
  vendor: 5.7
  cna: 9.1
ingestedAt: '2026-09-14T15:23:07.474Z'
---

## Overview

A flaw was found in the Linux kernel's Server Message Block (SMB) client. A remote malicious SMB server could send a specially crafted tree connect response with a byte count that is too small. This incorrect handling can lead to an integer underflow, causing the client to read beyond an allocated memory buffer. Consequently, sensitive information from kernel memory may be exposed to a local user through the `/proc/fs/cifs/DebugData` interface.

## Vendor advisories

- **Red Hat VEX** · Important · affected: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9, Red Hat OpenShift Container Platform 4 · no fix planned: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9, Red Hat OpenShift Container Platform 4 · updated 2026-09-18 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89631.json)

**kernel: smb: client: reject a tree connect response whose byte count is too small** — rated Important by Red Hat. Released 2026-09-11, updated 2026-09-18.

Affected:

- Red Hat Enterprise Linux 10
- Red Hat Enterprise Linux 8
- Red Hat Enterprise Linux 9
- Red Hat OpenShift Container Platform 4

No fix planned:

- Red Hat Enterprise Linux 10
- Red Hat Enterprise Linux 8
- Red Hat Enterprise Linux 9
- Red Hat OpenShift Container Platform 4

Not affected:

- Red Hat Enterprise Linux 6
- Red Hat Enterprise Linux 7

## Remediation

Affected