CVE-2026-6721: IBM Concert 1.0.0 through 3.0.0 allows an unauthenticated remote attacker can supply specially crafted input t

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CRITICAL 9.8REMOTEUPGRADE

CVE-2026-6721 is a critical-severity flaw (CVSS 9.8) affecting concert. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

IBM Concert 1.0.0 through 3.0.0 allows an unauthenticated remote attacker can supply specially crafted input that is incorporated into OS commands, resulting in arbitrary command execution on the underlying system. Successful exploitation allows remote code execution with the privileges of the affected application.

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	1.2% (top 32%)
CISA exploited list	No
Weakness	CWE-78
Published	2026-09-23
Last modified	2026-09-28

Publisher (CNA): IBM Corporation · Vendor: ibm

Last updated 2026-09-28 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-09-23 21:17 UTCPublished CVE record published
2026-09-28 20:45 UTCUpdated Record last modified

ibm concert UPGRADE

Affected: >= 1.0.0 and <= 3.0.0

Fixed in: newer than 3.0.0

Safe to downgrade to: a release before 1.0.0

1. Check installed version

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

2. UPGRADE to newer than 3.0.0 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade concert

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 1.0.0 (Debian / Ubuntu)

apt-cache madison concert sudo apt install concert=<VERSION_BEFORE_1.0.0> sudo apt-mark hold concert

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

dnf --showduplicates list concert sudo dnf downgrade concert-<VERSION_BEFORE_1.0.0> sudo dnf versionlock add concert

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 · fio · FIXED · 3.43-2.fc46 · FEDORA-2026-b36219886b · source

sudo dnf upgrade --advisory=FEDORA-2026-b36219886b

Fedora ELN · weston · FIXED · 16.0.2-1.eln159 · FEDORA-2026-b98ccaa6a0 · source

sudo dnf upgrade --advisory=FEDORA-2026-b98ccaa6a0

Public exploits and detection

Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.

Write-up: www.ibm.com/support/pages/node/7288830

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-2026-6721?

concert: upgrade to newer than 3.0.0. Exact commands for each OS are on this page.

Is CVE-2026-6721 being exploited?

CVE-2026-6721 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-2026-6721 affect?

CVE-2026-6721 affects concert. Severity is critical (CVSS 9.8). IBM Concert 1.0.0 through 3.0.0 allows an unauthenticated remote attacker can supply specially crafted input that is incorporated into OS commands, resulting in arbitrary command execution on the underlying system. Successful exploitation a

How urgent is CVE-2026-6721?

Priority 59/100. Critical severity; CISA SSVC: automatable with total technical impact; Remotely exploitable, no login, no user action

Related CVEs

CVE-2026-6928 CRITICAL 9.8 UPGRADE IBM Concert 1.0.0 through 3.0.0 references or accesses memory after it has been freed
CVE-2026-6935 HIGH 7.8 UPGRADE IBM Concert 1.0.0 through 3.0.0 invokes operating system commands without fully qualifying executable paths or
CVE-2026-6544 MEDIUM 6.2 UPGRADE IBM Concert 1.0.0 through 3.0.0 allows recursive copying of directories without proper controls which can lead
CVE-2026-6925 MEDIUM 5.3 UPGRADE IBM Concert 1.0.0 through 3.0.0 could allow a remote attacker to traverse directories on the system
CVE-2026-6794 HIGH 7.8 UPGRADE IBM Concert 1.0.0 through 3.0.0 has a double free vulnerability that exists due to incorrect memory management

References

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