---
id: CVE-2026-89651
title: >-
  kernel: ceph: bound MDSCapAuth path and fs_name decode in handle_session()
  (CVE-2026-89651)
summary: >-
  A flaw was found in the Linux kernel's Ceph client. An out-of-bounds read
  vulnerability exists in the `handle_session()` function when decoding
  `MDSCapAuth` records. A malicious or compromised Metadata Server (MDS) can
  trigger this during …
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
published: '2026-09-11'
updated: '2026-09-18'
sourceUpdated: '2026-09-18T20:12:22+00:00'
source: CSAF
sourceUrl: 'https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89651.json'
references:
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89651.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-89651'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2532282'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-89651'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-89651'
  - url: >-
      https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-89651.mbox
  - url: 'https://git.kernel.org/stable/c/5f892c767b30e4fb0c744c59f9235c717383d2cd'
  - url: 'https://git.kernel.org/stable/c/77933e22adfe813be2bd10be08d6e950103c3967'
  - url: 'https://git.kernel.org/stable/c/c37db86d2b5e9b57001ccae7e7a727e95a4f9c02'
  - url: 'https://git.kernel.org/stable/c/dc5c7dffda92ef372fa587c444a1c537373df824'
tags:
  - csaf
  - vex
  - red-hat
  - cve.org
  - score-dispute
epss: 0.00671
epssPercentile: 0.49862
scores:
  vendor: 5.9
  cna: 9.8
ingestedAt: '2026-09-14T15:23:07.473Z'
---

## Overview

A flaw was found in the Linux kernel's Ceph client. An out-of-bounds read vulnerability exists in the `handle_session()` function when decoding `MDSCapAuth` records. A malicious or compromised Metadata Server (MDS) can trigger this during session setup without client-side user interaction. This can force the kernel client to read past the message buffer, leading to a client crash and a Denial of Service (DoS).

## Vendor advisories

- **Red Hat VEX** · Moderate · affected: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 9 · no fix planned: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 9 · updated 2026-09-18 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89651.json)

**kernel: ceph: bound MDSCapAuth path and fs_name decode in handle_session()** — rated Moderate by Red Hat. Released 2026-09-11, updated 2026-09-18.

Affected:

- Red Hat Enterprise Linux 10
- Red Hat Enterprise Linux 9

No fix planned:

- Red Hat Enterprise Linux 10
- Red Hat Enterprise Linux 9

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