CVE-2021-33176: VerneMQ MQTT Broker versions prior to 1.12.0 are vulnerable to a denial of service attack as a result of exces

Q: How do I fix CVE-2021-33176?

vernemq: upgrade to 1.12.0. Exact commands for each OS are on this page.

Q: Is CVE-2021-33176 being exploited?

CVE-2021-33176 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-2021-33176 affect?

CVE-2021-33176 affects vernemq. Severity is high (CVSS 7.5). VerneMQ MQTT Broker versions prior to 1.12.0 are vulnerable to a denial of service attack as a result of excessive memory consumption due to the handling of untrusted inputs. These inputs cause the message broker to consume large amounts of

Q: How urgent is CVE-2021-33176?

Priority 48/100. High severity; Remotely exploitable, no login, no user action

This month

HIGH 7.5REMOTEUPGRADE

CVE-2021-33176 is a high-severity flaw (CVSS 7.5) affecting vernemq. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

VerneMQ MQTT Broker versions prior to 1.12.0 are vulnerable to a denial of service attack as a result of excessive memory consumption due to the handling of untrusted inputs. These inputs cause the message broker to consume large amounts of memory, resulting in the application being terminated by the operating system.

Why this priority

High severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	1.1% (top 34%)
CISA exploited list	No
Weakness	CWE-502, CWE-770
Published	2021-06-08
Last modified	2026-06-17

Publisher (CNA): Synopsys · Vendor: octavolabs

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

Am I affected?

Timeline

2021-06-08 15:15 UTCPublished CVE record published
2026-06-17 03:54 UTCUpdated Record last modified

octavolabs vernemq UPGRADE

Affected: < 1.12.0

Fixed in: 1.12.0

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to 1.12.0 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade vernemq

Note

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

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-2021-33176?

vernemq: upgrade to 1.12.0. Exact commands for each OS are on this page.

Is CVE-2021-33176 being exploited?

CVE-2021-33176 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-2021-33176 affect?

CVE-2021-33176 affects vernemq. Severity is high (CVSS 7.5). VerneMQ MQTT Broker versions prior to 1.12.0 are vulnerable to a denial of service attack as a result of excessive memory consumption due to the handling of untrusted inputs. These inputs cause the message broker to consume large amounts of

How urgent is CVE-2021-33176?

Priority 48/100. High severity; Remotely exploitable, no login, no user action

References

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