---
id: CVE-2026-68155
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  libceph: Reject monmaps advertising zero monitors

  A message of type CEPH_MSG_MON_MAP contains a monmap that is sent from a
  monitor to the client
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  libceph: Reject monmaps advertising zero monitors

  A message of type CEPH_MSG_MON_MAP contains a monmap that is sent from a
  monitor to the client. This monmap contains …
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'
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= ba75bb98cfb93b62c54af25bf67ff90857264bbe <
    ba5f0015bfd376d764163045a61c17be75f44dae
  - >-
    Linux >= ba75bb98cfb93b62c54af25bf67ff90857264bbe <
    caf082ef8609a6ac26159ce115f55ab7d00231a3
  - >-
    Linux >= ba75bb98cfb93b62c54af25bf67ff90857264bbe <
    e3ccd4ecab09b22f507f49cb7ed9990c7158ceab
  - >-
    Linux >= ba75bb98cfb93b62c54af25bf67ff90857264bbe <
    0591a15815b498be628a937146e44487d599ba33
  - >-
    Linux >= ba75bb98cfb93b62c54af25bf67ff90857264bbe <
    cd0d41bc569632eaaeccde9d2a6bc919ec00c407
  - >-
    Linux >= ba75bb98cfb93b62c54af25bf67ff90857264bbe <
    e67e8b694872c9bc66996040f9de9242f6236ed9
  - >-
    Linux >= ba75bb98cfb93b62c54af25bf67ff90857264bbe <
    3b249546f59c3d6d3592c10657f82bc3f1faa07c
  - >-
    Linux >= ba75bb98cfb93b62c54af25bf67ff90857264bbe <
    40480eee361ed9676b3f844d532ac28b47251634
  - Linux 2.6.34
published: '2026-08-10'
updated: '2026-10-03'
sourceUpdated: '2026-10-03T11:17:35.793'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-68155'
references:
  - url: 'https://git.kernel.org/stable/c/0591a15815b498be628a937146e44487d599ba33'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/3b249546f59c3d6d3592c10657f82bc3f1faa07c'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/40480eee361ed9676b3f844d532ac28b47251634'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/ba5f0015bfd376d764163045a61c17be75f44dae'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/caf082ef8609a6ac26159ce115f55ab7d00231a3'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/cd0d41bc569632eaaeccde9d2a6bc919ec00c407'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/e3ccd4ecab09b22f507f49cb7ed9990c7158ceab'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/e67e8b694872c9bc66996040f9de9242f6236ed9'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
tags:
  - nvd
  - cve.org
epss: 0.0068
epssPercentile: 0.50667
ingestedAt: '2026-10-03T11:43:42.115Z'
---

## Overview

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

libceph: Reject monmaps advertising zero monitors

A message of type CEPH_MSG_MON_MAP contains a monmap that is sent from a
monitor to the client. This monmap contains information about the
existing monitors in the cluster. Currently, a monmap indicating that
there are zero monitors in the cluster is treated as valid. However, it
is impossible to have zero monitors in the cluster and still receive a
valid monmap from a monitor. Therefore, such a monmap must be corrupted
and should be treated as invalid. Furthermore, a monmap with a monitor
count of zero can subsequently crash the client when attempting to open
a session with a monitor in __open_session(). This happens because the
"BUG_ON(monc->monmap->num_mon < 1)" assertion in pick_new_mon() is
triggered.

This patch extends a check in ceph_monmap_decode() to also reject
arriving mon_maps with num_mon == 0 rather than only with
num_mon > CEPH_MAX_MON.

[ idryomov: drop "log output for unusual values of num_mon" part ]

## Remediation

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