CVE-2026-16840: IBM AIX 7.2, and 7.3 and IBM PowerVM VIOS 4.1 could allow a remote attacker to execute arbitrary code due to a

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CRITICAL 9.8REMOTEUPGRADEUPGRADE

CVE-2026-16840 is a critical-severity flaw (CVSS 9.8) affecting aix, vios. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

IBM AIX 7.2, and 7.3 and IBM PowerVM VIOS 4.1 could allow a remote attacker to execute arbitrary code due to an out-of-bounds write.

Why this priority

Critical severity
CISA SSVC: automatable with total technical impact
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.8% (top 44%)
CISA exploited list	No
Weakness	CWE-787
Published	2026-08-19
Last modified	2026-10-26

Publisher (CNA): IBM Corporation · Vendor: ibm

Last updated 2026-10-26 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-08-19 20:17 UTCPublished CVE record published
2026-10-26 10:10 UTCUpdated Record last modified

ibm aix UPGRADE

Affected: >= 7.2.5 and <= 7.2.5.212 · >= 7.3.2 and <= 7.3.2.5 · >= 7.3.3 and <= 7.3.3.2 · >= 7.3.4 and <= 7.3.4.1

Fixed in: newer than 7.3.4.1

Safe to downgrade to: a release before 7.2.5

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.

ibm vios UPGRADE

Affected: >= 4.1.0 and < 4.1.0.50 · >= 4.1.1.0 and < 4.1.1.30 · >= 4.1.2.0 and < 4.1.2.20

Fixed in: 4.1.0.50, 4.1.1.30, 4.1.2.20

Safe to downgrade to: a release before 4.1.0

1. Check installed version

apt-cache policy vios || rpm -q vios || vios --version

2. UPGRADE to 4.1.0.50 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade vios

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade vios

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 4.1.0 (Debian / Ubuntu)

apt-cache madison vios sudo apt install vios=<VERSION_BEFORE_4.1.0> sudo apt-mark hold vios

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list vios sudo dnf downgrade vios-<VERSION_BEFORE_4.1.0> sudo dnf versionlock add vios

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Exact fixes by distribution

Fedora 46 · mac · FIXED · 13.43-1.fc46 · FEDORA-2026-8fac5b22cf · source

sudo dnf upgrade --advisory=FEDORA-2026-8fac5b22cf

Fedora ELN · libdnf · FIXED · 0.76.0-2.eln159 · FEDORA-2026-dbd263e9d4 · source

sudo dnf upgrade --advisory=FEDORA-2026-dbd263e9d4

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-2026-16840?

aix: upgrade to newer than 7.3.4.1; vios: upgrade to 4.1.0.50, 4.1.1.30, 4.1.2.20. Exact commands for each OS are on this page.

Is CVE-2026-16840 being exploited?

CVE-2026-16840 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-2026-16840 affect?

CVE-2026-16840 affects aix, vios. Severity is critical (CVSS 9.8). IBM AIX 7.2, and 7.3 and IBM PowerVM VIOS 4.1 could allow a remote attacker to execute arbitrary code due to an out-of-bounds write.

How urgent is CVE-2026-16840?

Priority 56/100. Critical severity; CISA SSVC: automatable with total technical impact; Remotely exploitable, no login, no user action

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References

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