CVE-2023-5632Public exploitNetwork attack vector

Denial of service via unconditional EPOLLOUT registration

Published Oct 18, 2023 · Updated Sep 13, 2024

Denial of service in Eclipse Mosquitto 2.0.5 and earlier allows remote attackers to consume broker CPU via an idle connection. In packet__write, the broker registered EPOLLOUT even when current_out_packet was null, so epoll_wait returned continuously instead of blocking. No authentication or transmitted MQTT data is required, and a held-open connection drives the event loop until timeout.

CVSS severity7.5
High
EPSS probability0.69%
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 Eclipse Mosquitto 2.0.5 and earlier allows remote attackers to consume broker CPU via an idle connection. In packet__write, the broker registered EPOLLOUT even when current_out_packet was null, so epoll_wait returned continuously instead of blocking. No authentication or transmitted MQTT data is required, and a held-open connection drives the event loop until timeout.

The record

CVE
CVE-2023-5632
Published
Oct 18, 2023
Updated
Sep 13, 2024
Vendor
The Eclipse Foundation
Product
Eclipse Mosquitto
Classifications
CWE-834, CAPEC-130, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 18, 2023CVE publishedPublication date reported by the CVE source.
  2. Sep 13, 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=0 <=2.0.5

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Eclipse Foundation · Eclipse Mosquittoversion=0 <=2.0.5

Published CVSS scores

7.5Eclipse FoundationCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

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 exploitPublished

Weakness, pattern, technique

CWE-834Excessive Iteration
CAPEC-130Excessive Allocation
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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