---
id: CVE-2026-43405
title: 'libceph: Use u32 for non-negative values in ceph_monmap_decode()'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  libceph: Use u32 for non-negative values in ceph_monmap_decode()

  This patch fixes unnecessary implicit conversions that change signedness
  of blob_len and num_mon in ce…
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
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= a5cbd5fc22d5043a8a76e15d75d031fe24d1f69c <
    ee5588e2bc41acb73f6676c0520420c107cd0140
  - >-
    Linux >= a5cbd5fc22d5043a8a76e15d75d031fe24d1f69c <
    86f7060cd638d6eb042e8ed780fb83a59ca0dcb3
  - >-
    Linux >= a5cbd5fc22d5043a8a76e15d75d031fe24d1f69c <
    5f2806684b05bd24d05c091083b8e2517ba8ffac
  - >-
    Linux >= a5cbd5fc22d5043a8a76e15d75d031fe24d1f69c <
    b268984ae88cb0dcd7a8e8263962c748448e26e8
  - >-
    Linux >= a5cbd5fc22d5043a8a76e15d75d031fe24d1f69c <
    ba0a4df8c563536857dcbf7b4dbd0f2a15f57ace
  - >-
    Linux >= a5cbd5fc22d5043a8a76e15d75d031fe24d1f69c <
    08bc6173fd611ad5a40f472bf5f15b92aea0fe40
  - >-
    Linux >= a5cbd5fc22d5043a8a76e15d75d031fe24d1f69c <
    770444611f047dbfd4517ec0bc1b179d40c2f346
  - Linux 5.11
ssvc:
  exploitation: none
  automatable: 'yes'
  technicalImpact: partial
  timestamp: '2026-10-16T15:17:06.278684Z'
published: '2026-05-08'
updated: '2026-10-16'
sourceUpdated: '2026-10-16T15:20:40.951Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-43405'
references:
  - url: 'https://git.kernel.org/stable/c/ee5588e2bc41acb73f6676c0520420c107cd0140'
  - url: 'https://git.kernel.org/stable/c/86f7060cd638d6eb042e8ed780fb83a59ca0dcb3'
  - url: 'https://git.kernel.org/stable/c/5f2806684b05bd24d05c091083b8e2517ba8ffac'
  - url: 'https://git.kernel.org/stable/c/b268984ae88cb0dcd7a8e8263962c748448e26e8'
  - url: 'https://git.kernel.org/stable/c/ba0a4df8c563536857dcbf7b4dbd0f2a15f57ace'
  - url: 'https://git.kernel.org/stable/c/08bc6173fd611ad5a40f472bf5f15b92aea0fe40'
  - url: 'https://git.kernel.org/stable/c/770444611f047dbfd4517ec0bc1b179d40c2f346'
tags:
  - cve.org
epss: 0.007
epssPercentile: 0.52217
ingestedAt: '2026-10-16T17:24:46.694Z'
---

## Overview

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

libceph: Use u32 for non-negative values in ceph_monmap_decode()

This patch fixes unnecessary implicit conversions that change signedness
of blob_len and num_mon in ceph_monmap_decode().
Currently blob_len and num_mon are (signed) int variables. They are used
to hold values that are always non-negative and get assigned in
ceph_decode_32_safe(), which is meant to assign u32 values. Both
variables are subsequently used as unsigned values, and the value of
num_mon is further assigned to monmap->num_mon, which is of type u32.
Therefore, both variables should be of type u32. This is especially
relevant for num_mon. If the value read from the incoming message is
very large, it is interpreted as a negative value, and the check for
num_mon > CEPH_MAX_MON does not catch it. This leads to the attempt to
allocate a very large chunk of memory for monmap, which will most likely
fail. In this case, an unnecessary attempt to allocate memory is
performed, and -ENOMEM is returned instead of -EINVAL.

## Affected

- `Linux >= a5cbd5fc22d5043a8a76e15d75d031fe24d1f69c < ee5588e2bc41acb73f6676c0520420c107cd0140`
- `Linux >= a5cbd5fc22d5043a8a76e15d75d031fe24d1f69c < 86f7060cd638d6eb042e8ed780fb83a59ca0dcb3`
- `Linux >= a5cbd5fc22d5043a8a76e15d75d031fe24d1f69c < 5f2806684b05bd24d05c091083b8e2517ba8ffac`
- `Linux >= a5cbd5fc22d5043a8a76e15d75d031fe24d1f69c < b268984ae88cb0dcd7a8e8263962c748448e26e8`
- `Linux >= a5cbd5fc22d5043a8a76e15d75d031fe24d1f69c < ba0a4df8c563536857dcbf7b4dbd0f2a15f57ace`
- `Linux >= a5cbd5fc22d5043a8a76e15d75d031fe24d1f69c < 08bc6173fd611ad5a40f472bf5f15b92aea0fe40`
- `Linux >= a5cbd5fc22d5043a8a76e15d75d031fe24d1f69c < 770444611f047dbfd4517ec0bc1b179d40c2f346`
- `Linux 5.11`

## Remediation

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