CVE-2020-13821: An issue was discovered in HiveMQ Broker Control Center 4.3.2

Routine

MEDIUM 5.4DOWNGRADE

CVE-2020-13821 is a medium-severity flaw (CVSS 5.4) affecting broker control center. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

An issue was discovered in HiveMQ Broker Control Center 4.3.2. A crafted clientid parameter in an MQTT packet (sent to the Broker) is reflected in the client section of the management console. The attacker's JavaScript is loaded in a browser, which can lead to theft of the session and cookie of the administrator's account of the Broker.

Why this priority

No elevated risk signals yet

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	5.4 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	Required
EPSS exploit chance	0.5% (top 55%)
CISA exploited list	No
Weakness	CWE-79
Published	2020-08-26
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: hivemq

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2020-08-26 16:15 UTCPublished CVE record published
2026-06-17 02:53 UTCUpdated Record last modified

hivemq broker control center DOWNGRADE

Affected: 4.3.2

Fixed in: no fixed release known

Safe to downgrade to: a release before 4.3.2

1. Check installed version

apt-cache policy broker-control-center || rpm -q broker-control-center || broker-control-center --version

2. No fixed release: DOWNGRADE to a release before 4.3.2 (Debian / Ubuntu)

apt-cache madison broker-control-center sudo apt install broker-control-center=<VERSION_BEFORE_4.3.2> sudo apt-mark hold broker-control-center

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list broker-control-center sudo dnf downgrade broker-control-center-<VERSION_BEFORE_4.3.2> sudo dnf versionlock add broker-control-center

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-2020-13821?

broker control center: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2020-13821 being exploited?

CVE-2020-13821 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-2020-13821 affect?

CVE-2020-13821 affects broker control center. Severity is medium (CVSS 5.4). An issue was discovered in HiveMQ Broker Control Center 4.3.2. A crafted clientid parameter in an MQTT packet (sent to the Broker) is reflected in the client section of the management console. The attacker's JavaScript is loaded in a browse

How urgent is CVE-2020-13821?

Priority 30/100. No elevated risk signals yet.

References

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