---
id: CVE-2026-89657
title: 'libceph: validate OSD extent maps before cursor advance'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  libceph: validate OSD extent maps before cursor advance

  net/ceph/osd_client.c:osd_sparse_read() validates that the sparse-read
  data length matches the summed extent le…
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'
cvssSource: cna
cwe:
  - CWE-125
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= f628d799972799023d32c2542bb2639eb8c4f84e <
    94ae5145c520618802b0a24c047dcd5f05835db8
  - >-
    Linux >= f628d799972799023d32c2542bb2639eb8c4f84e <
    058ffa81f9440c5b4714685611cf697fd3739ec9
  - >-
    Linux >= f628d799972799023d32c2542bb2639eb8c4f84e <
    2571b35883268a266554e80d368e67fdfea7fb9d
  - >-
    Linux >= f628d799972799023d32c2542bb2639eb8c4f84e <
    201db408872ca12cf09e36bf0f560138c3dcfa1c
  - >-
    Linux >= f628d799972799023d32c2542bb2639eb8c4f84e <
    9ec08b7499a62c6d4afa93d36ab47a43fcad57d1
  - Linux 6.6
published: '2026-09-11'
updated: '2026-10-19'
sourceUpdated: '2026-10-19T08:50:28.836Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-89657'
references:
  - url: 'https://git.kernel.org/stable/c/94ae5145c520618802b0a24c047dcd5f05835db8'
  - url: 'https://git.kernel.org/stable/c/058ffa81f9440c5b4714685611cf697fd3739ec9'
  - url: 'https://git.kernel.org/stable/c/2571b35883268a266554e80d368e67fdfea7fb9d'
  - url: 'https://git.kernel.org/stable/c/201db408872ca12cf09e36bf0f560138c3dcfa1c'
  - url: 'https://git.kernel.org/stable/c/9ec08b7499a62c6d4afa93d36ab47a43fcad57d1'
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89657.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-89657'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2532301'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-89657'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-89657'
  - url: >-
      https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-89657.mbox
tags:
  - cve.org
  - csaf
  - vex
  - red-hat
epss: 0.00612
epssPercentile: 0.49084
scores:
  cna: 7.5
  vendor: 7
ingestedAt: '2026-09-14T15:23:07.450Z'
---

## Overview

In the Linux kernel, the following vulnerability has been resolved:

libceph: validate OSD extent maps before cursor advance

net/ceph/osd_client.c:osd_sparse_read() validates that the sparse-read
data length matches the summed extent lengths, but it does not validate
that each OSD-supplied extent is monotonic and lies inside the original
request range. A malformed authenticated OSD reply can advertise a
far-forward nonzero extent offset with a matching data length and make
the client advance the message-data cursor beyond the request buffer.
This reaches the BUG_ON(!*length) assertion in ceph_msg_data_next() from
the client receive path.

Impact: A malicious or compromised authenticated Ceph OSD peer can crash
a kernel Ceph client via a malformed sparse-read reply.

Reject sparse extent maps that overflow, move backwards, overlap, or
extend outside the original sparse-read request before advancing the
cursor.

[ idryomov: perform sparse_extent_map_valid() check a bit earlier,
  in CEPH_SPARSE_READ_DATA_LEN instead of CEPH_SPARSE_READ_DATA_PRE
  state ]

## Affected

- `Linux >= f628d799972799023d32c2542bb2639eb8c4f84e < 94ae5145c520618802b0a24c047dcd5f05835db8`
- `Linux >= f628d799972799023d32c2542bb2639eb8c4f84e < 058ffa81f9440c5b4714685611cf697fd3739ec9`
- `Linux >= f628d799972799023d32c2542bb2639eb8c4f84e < 2571b35883268a266554e80d368e67fdfea7fb9d`
- `Linux >= f628d799972799023d32c2542bb2639eb8c4f84e < 201db408872ca12cf09e36bf0f560138c3dcfa1c`
- `Linux >= f628d799972799023d32c2542bb2639eb8c4f84e < 9ec08b7499a62c6d4afa93d36ab47a43fcad57d1`
- `Linux 6.6`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

## Vendor advisories

- **Red Hat VEX** · Moderate · 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-2026-89657.json)