CVE-2026-4370: A vulnerability was identified in Juju from version 3.2.0 until 3.6.19 and from version 4.0 until 4.0.4, where

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CRITICAL 10.0REMOTEUPGRADE

CVE-2026-4370 is a critical-severity flaw (CVSS 10.0) affecting juju. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A vulnerability was identified in Juju from version 3.2.0 until 3.6.19 and from version 4.0 until 4.0.4, where the internal Dqlite database cluster fails to perform proper TLS client and server authentication. Specifically, the Juju controller's database endpoint does not validate client certificates when a new node attempts to join the cluster. An unauthenticated attacker with network reachability to the Juju controller's Dqlite port can exploit

Why this priority

Critical severity
Public exploit reference
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	10.0 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.4% (top 68%)
CISA exploited list	No
Weakness	CWE-295, CWE-306
Published	2026-04-01
Last modified	2026-10-26

Publisher (CNA): Canonical Ltd. · Vendor: canonical

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

Am I affected?

Timeline

2026-04-01 09:16 UTCPublished CVE record published
2026-10-26 21:10 UTCUpdated Record last modified

canonical juju UPGRADE

Affected: >= 3.2.0 and < 3.6.20 · >= 4.0 and < 4.0.5

Fixed in: 3.6.20, 4.0.5

Safe to downgrade to: a release before 3.2.0

1. Check installed version

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

2. UPGRADE to 3.6.20 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade juju

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 3.2.0 (Debian / Ubuntu)

apt-cache madison juju sudo apt install juju=<VERSION_BEFORE_3.2.0> sudo apt-mark hold juju

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

dnf --showduplicates list juju sudo dnf downgrade juju-<VERSION_BEFORE_3.2.0> sudo dnf versionlock add juju

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.

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-2026-4370?

juju: upgrade to 3.6.20, 4.0.5. Exact commands for each OS are on this page.

Is CVE-2026-4370 being exploited?

CVE-2026-4370 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-2026-4370 affect?

CVE-2026-4370 affects juju. Severity is critical (CVSS 10.0). A vulnerability was identified in Juju from version 3.2.0 until 3.6.19 and from version 4.0 until 4.0.4, where the internal Dqlite database cluster fails to perform proper TLS client and server authentication. Specifically, the Juju control

How urgent is CVE-2026-4370?

Priority 53/100. Critical severity; Public exploit reference; Remotely exploitable, no login, no user action

Related CVEs

CVE-2026-5412 CRITICAL 9.9 UPGRADE In Juju versions prior to 2.9.57 and 3.6.21, an authorization issue exists in the Controller facade
CVE-2026-5774 MEDIUM 6.4 UPGRADE Improper synchronization of the userTokens map in the API server in Canonical Juju 4.0.5, 3.6.20, and 2.9.56 m

References

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