CVE-2026-43405Network attack vector

Service interruption via monitor-count signedness conversion

Published May 8, 2026 · Updated May 8, 2026

Denial of service in the Linux Kernel Ceph client allows remote attackers to interrupt service via a crafted monitor map message. ceph_monmap_decode stores the unsigned num_mon field in a signed int, so a large value becomes negative, bypasses the CEPH_MAX_MON bound, and drives an oversized monmap allocation. A target must use the kernel Ceph client and decode an attacker-controlled monitor map; the documented outcome is allocation failure and an incorrect error return, not code execution or data access.

CVSS severity7.5
High
EPSS probability0.49%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in the Linux Kernel Ceph client allows remote attackers to interrupt service via a crafted monitor map message. ceph_monmap_decode stores the unsigned num_mon field in a signed int, so a large value becomes negative, bypasses the CEPH_MAX_MON bound, and drives an oversized monmap allocation. A target must use the kernel Ceph client and decode an attacker-controlled monitor map; the documented outcome is allocation failure and an incorrect error return, not code execution or data access.

The record

CVE
CVE-2026-43405
Published
May 8, 2026
Updated
May 8, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
CWE-908, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 8, 2026CVE publishedPublication date reported by the CVE source.
  2. May 8, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <08bc6173fd611ad5a40f472bf5f15b92aea0fe40
  2. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <5f2806684b05bd24d05c091083b8e2517ba8ffac
  3. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <770444611f047dbfd4517ec0bc1b179d40c2f346
  4. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <86f7060cd638d6eb042e8ed780fb83a59ca0dcb3
  5. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <b268984ae88cb0dcd7a8e8263962c748448e26e8
  6. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <ba0a4df8c563536857dcbf7b4dbd0f2a15f57ace
  7. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <ee5588e2bc41acb73f6676c0520420c107cd0140

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <08bc6173fd611ad5a40f472bf5f15b92aea0fe40; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <5f2806684b05bd24d05c091083b8e2517ba8ffac; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <770444611f047dbfd4517ec0bc1b179d40c2f346; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <86f7060cd638d6eb042e8ed780fb83a59ca0dcb3; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <b268984ae88cb0dcd7a8e8263962c748448e26e8; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <ba0a4df8c563536857dcbf7b4dbd0f2a15f57ace; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <ee5588e2bc41acb73f6676c0520420c107cd0140

Published CVSS scores

7.5kernel.orgCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-908Use of Uninitialized Resource
T1499.004Endpoint Denial of Service: Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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