---
id: CVE-2026-89633
title: >-
  kernel: smb: client: fix OOB read/write from unvalidated DataOffset in
  coalesce_t2() (CVE-2026-89633)
summary: >-
  A flaw was found in the Linux kernel's Server Message Block (SMB) client. The
  `coalesce_t2()` function processes server-supplied `DataOffset` fields without
  proper validation against buffer boundaries. A remote attacker could exploit
  this …
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 9
  - openshift_container_platform 4
published: '2026-09-11'
updated: '2026-09-18'
sourceUpdated: '2026-09-18T20:18:38+00:00'
source: CSAF
sourceUrl: 'https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89633.json'
references:
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89633.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-89633'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2532230'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-89633'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-89633'
  - url: >-
      https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-89633.mbox
  - url: 'https://git.kernel.org/stable/c/033bc80019f07d158630df4e69b19a49010f54f1'
  - url: 'https://git.kernel.org/stable/c/6343c1da561962688f203362d80d6a3bfa39fa1b'
  - url: 'https://git.kernel.org/stable/c/672cf86aa6aa0fb4012ce4c3b3498df42ad67a4e'
tags:
  - csaf
  - vex
  - red-hat
  - cve.org
  - score-dispute
epss: 0.00481
epssPercentile: 0.40622
scores:
  vendor: 7.1
  cna: 9.8
ingestedAt: '2026-09-14T15:23:07.474Z'
---

## Overview

A flaw was found in the Linux kernel's Server Message Block (SMB) client. The `coalesce_t2()` function processes server-supplied `DataOffset` fields without proper validation against buffer boundaries. A remote attacker could exploit this by crafting malicious SMB responses. This could lead to out-of-bounds read and write operations, potentially resulting in information disclosure or arbitrary code execution.

## Vendor advisories

- **Red Hat VEX** · Important · affected: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 9, Red Hat OpenShift Container Platform 4 · no fix planned: Red Hat Enterprise Linux 10, 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-2026-89633.json)

**kernel: smb: client: fix OOB read/write from unvalidated DataOffset in coalesce_t2()** — rated Important by Red Hat. Released 2026-09-11, updated 2026-09-18.

Affected:

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

No fix planned:

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

Not affected:

- Red Hat Enterprise Linux 6
- Red Hat Enterprise Linux 7
- Red Hat Enterprise Linux 8
- Red Hat OpenShift Container Platform 4

## Remediation

Affected