CVE-2024-35512Network attack vector

Broker crash via malformed UNSUBSCRIBE topic

Published May 29, 2024 · Updated Apr 16, 2026

Denial of service in FHMQ HMQ 1.5.5 allows remote attackers to crash the broker via a malformed MQTT UNSUBSCRIBE packet. The UNSUBSCRIBE topic parser fails to reject an illegal control character, produces a nil value, and dereferences it, terminating the process. No authentication or user interaction is required, and a successful request immediately interrupts service for every connected MQTT client.

CVSS severity5.3
Medium
EPSS probability0.46%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in FHMQ HMQ 1.5.5 allows remote attackers to crash the broker via a malformed MQTT UNSUBSCRIBE packet. The UNSUBSCRIBE topic parser fails to reject an illegal control character, produces a nil value, and dereferences it, terminating the process. No authentication or user interaction is required, and a successful request immediately interrupts service for every connected MQTT client.

The record

CVE
CVE-2024-35512
Published
May 29, 2024
Updated
Apr 16, 2026
Vendor
FHMQ
Product
HMQ
Classifications
T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 29, 2024CVE publishedPublication date reported by the CVE source.
  2. Apr 16, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=1.5.5

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

FHMQ · HMQversion=1.5.5

Published CVSS scores

5.3CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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