CVE-2021-41039Public exploitNetwork attack vector

Broker denial of service via quadratic property checks

Published Dec 1, 2021 · Updated Aug 4, 2024

Resource exhaustion in Eclipse Mosquitto 1.6 through 2.0.11 allows remote attackers to interrupt broker service via an MQTT v5 CONNECT packet. The mosquitto_property_check_all function compares each property with later entries even for repeatable User Properties, producing quadratic CPU work on a long list. A network-reachable MQTT v5 listener is sufficient, and the bounded consequence is CPU exhaustion that delays or denies broker service without data access or modification.

CVSS severity7.5
High
EPSS probability1.26%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Resource exhaustion in Eclipse Mosquitto 1.6 through 2.0.11 allows remote attackers to interrupt broker service via an MQTT v5 CONNECT packet. The mosquitto_property_check_all function compares each property with later entries even for repeatable User Properties, producing quadratic CPU work on a long list. A network-reachable MQTT v5 listener is sufficient, and the bounded consequence is CPU exhaustion that delays or denies broker service without data access or modification.

The record

CVE
CVE-2021-41039
Published
Dec 1, 2021
Updated
Aug 4, 2024
Vendor
The Eclipse Foundation
Product
Eclipse Mosquitto
Classifications
CWE-1050, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Dec 1, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record 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=1.6 <unspecified
  2. Affected versionversion=unspecified <=2.0.11

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Eclipse Foundation · Eclipse Mosquittoversion=1.6 <unspecified; version=unspecified <=2.0.11

Published CVSS scores

7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:N/A:P

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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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 exploitPublished

Weakness, pattern, technique

CWE-1050Excessive Platform Resource Consumption within a Loop
T1499.004Application or System Exploitation

Public exploit references

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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