CVE-2026-43406: In the Linux kernel, the following vulnerability has been resolved: libceph: prevent potential out-of-bounds

Q: How do I fix CVE-2026-43406?

linux kernel: upgrade to 5.15.203, 6.1.167, 6.6.130, 6.12.78, 6.18.19, 6.19.9. Exact commands for each OS are on this page.

Q: Is CVE-2026-43406 being exploited?

CVE-2026-43406 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-43406 affect?

CVE-2026-43406 affects linux kernel. Severity is critical (CVSS 9.1). In the Linux kernel, the following vulnerability has been resolved: libceph: prevent potential out-of-bounds reads in process_message_header() If the message frame is (maliciously) corrupted in a way that the length of the control segment

Q: How urgent is CVE-2026-43406?

Priority 54/100. Critical severity; Remotely exploitable, no login, no user action; On your watchlist

This month

CRITICAL 9.1REMOTEWATCHLISTUPGRADE

CVE-2026-43406 is a critical-severity flaw (CVSS 9.1) affecting linux kernel. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

In the Linux kernel, the following vulnerability has been resolved: libceph: prevent potential out-of-bounds reads in process_message_header() If the message frame is (maliciously) corrupted in a way that the length of the control segment ends up being less than the size of the message header or a different frame is made to look like a message frame, out-of-bounds reads may ensue in process_message_header(). Perform an explicit bounds check be

Why this priority

Critical severity
Remotely exploitable, no login, no user action
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	9.1 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.6% (top 51%)
CISA exploited list	No
Weakness	CWE-125
Published	2026-05-08
Last modified	2026-10-19

Publisher (CNA): kernel.org · Vendor: linux

Last updated 2026-10-19 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-05-08 15:16 UTCPublished CVE record published
2026-10-19 20:18 UTCUpdated Record last modified

linux linux kernel UPGRADE

Affected: >= 5.11 and < 5.15.203 · >= 5.16 and < 6.1.167 · >= 6.2 and < 6.6.130 · >= 6.7 and < 6.12.78 · >= 6.13 and < 6.18.19 · >= 6.19 and < 6.19.9 · 7.0 rc1 · 7.0 rc2

Fixed in: 5.15.203, 6.1.167, 6.6.130, 6.12.78, 6.18.19, 6.19.9

Safe to downgrade to: no unaffected older release

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

Exact fixes by distribution

Fedora 46 · fzssh · FIXED · 1.4.0-2.fc46 · FEDORA-2026-8004fcd067 · source

sudo dnf upgrade --advisory=FEDORA-2026-8004fcd067

Ubuntu 22.04 · linux · FIXED · 5.15.0-185.195

sudo apt update && sudo apt install --only-upgrade linux dpkg --compare-versions "$(dpkg-query -W -f='${Version}' linux)" ge "5.15.0-185.195" && echo PATCHED || echo STILL-VULNERABLE

Ubuntu 24.04 · linux · FIXED · 6.8.0-134.134

sudo apt update && sudo apt install --only-upgrade linux dpkg --compare-versions "$(dpkg-query -W -f='${Version}' linux)" ge "6.8.0-134.134" && echo PATCHED || echo STILL-VULNERABLE

Ubuntu 25.10 · linux · FIXED · 6.17.0-40.40

sudo apt update && sudo apt install --only-upgrade linux dpkg --compare-versions "$(dpkg-query -W -f='${Version}' linux)" ge "6.17.0-40.40" && echo PATCHED || echo STILL-VULNERABLE

Ubuntu 20.04 · linux · NOT AFFECTED

Ubuntu 20.04 · linux-hwe-5.15 · FIXED · 5.15.0-185.195~20.04.1

sudo apt update && sudo apt install --only-upgrade linux-hwe-5.15 dpkg --compare-versions "$(dpkg-query -W -f='${Version}' linux-hwe-5.15)" ge "5.15.0-185.195~20.04.1" && echo PATCHED || echo STILL-VULNERABLE

Debian 12 · linux · FIXED · 6.1.170-1

sudo apt update && sudo apt install --only-upgrade linux dpkg --compare-versions "$(dpkg-query -W -f='${Version}' linux)" ge "6.1.170-1" && echo PATCHED || echo STILL-VULNERABLE

Debian 13 · linux · FIXED · 6.12.85-1

sudo apt update && sudo apt install --only-upgrade linux dpkg --compare-versions "$(dpkg-query -W -f='${Version}' linux)" ge "6.12.85-1" && echo PATCHED || echo STILL-VULNERABLE

RHEL 10 · kernel · DEFERRED

RHEL 6 · kernel · NOT AFFECTED

RHEL 7 · kernel · NOT AFFECTED

RHEL 7 · kernel-rt · NOT AFFECTED

RHEL 8 · kernel · DEFERRED

Amazon Linux 2023 · see advisory · FIXED · ALAS2023-2026-1681 · source

sudo dnf update --advisory=ALAS2023-2026-1681

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-43406?

linux kernel: upgrade to 5.15.203, 6.1.167, 6.6.130, 6.12.78, 6.18.19, 6.19.9. Exact commands for each OS are on this page.

Is CVE-2026-43406 being exploited?

CVE-2026-43406 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-43406 affect?

CVE-2026-43406 affects linux kernel. Severity is critical (CVSS 9.1). In the Linux kernel, the following vulnerability has been resolved: libceph: prevent potential out-of-bounds reads in process_message_header() If the message frame is (maliciously) corrupted in a way that the length of the control segment

How urgent is CVE-2026-43406?

Priority 54/100. Critical severity; Remotely exploitable, no login, no user action; On your watchlist

Software pages

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References

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