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CVE-2021-41039

In versions 1.6 to 2.0.11 of Eclipse Mosquitto, an MQTT v5 client connecting with a large number...

7.5 HighFix available

In versions 1.6 to 2.0.11 of Eclipse Mosquitto, an MQTT v5 client connecting with a large number of user-property properties could cause excessive CPU usage, leading to a loss of performance and possible denial of service.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
None
Integrity
None
Availability
High

Exploit likelihood

1.35%Up 0.8 points since Dec 2, 2021
90%50%10%1%

What each source reports

NVD Score used 7.5

In versions 1.6 to 2.0.11 of Eclipse Mosquitto, an MQTT v5 client connecting with a large number of user-property properties could cause excessive CPU usage, leading to a loss of performance and possible denial of service.

Record
CVE-2021-41039
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CVSS 2.0
5.0 MediumAV:N/AC:L/Au:N/C:N/I:N/A:P
Weakness
CWE-1050
Updated
2026-11-02
CVE List No score

In versions 1.6 to 2.0.11 of Eclipse Mosquitto, an MQTT v5 client connecting with a large number of user-property properties could cause excessive CPU usage, leading to a loss of performance and possible denial of service.

Record
CVE-2021-41039
Weakness
CWE-1050
Updated
2026-11-02
EUVDEUVD-2021-28191 No score

In versions 1.6 to 2.0.11 of Eclipse Mosquitto, an MQTT v5 client connecting with a large number of user-property properties could cause excessive CPU usage, leading to a loss of performance and possible denial of service.

Record
EUVD-2021-28191
Updated
2026-11-03
GitHub AdvisoriesGHSA-5xp2-36v8-r67m 7.5

In versions 1.6 to 2.0.11 of Eclipse Mosquitto, an MQTT v5 client connecting with a large number...

In versions 1.6 to 2.0.11 of Eclipse Mosquitto, an MQTT v5 client connecting with a large number of user-property properties could cause excessive CPU usage, leading to a loss of performance and possible denial of service.

Record
GHSA-5xp2-36v8-r67m
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness
CWE-1050
Updated
2026-11-02
OSVBELL-CVE-2021-41039 7.5

CVE-2021-41039 does not affect BellSoft software

Record
BELL-CVE-2021-41039
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02
OSV 7.5

In versions 1.6 to 2.0.11 of Eclipse Mosquitto, an MQTT v5 client connecting with a large number of user-property properties could cause excessive CPU usage, leading to a loss of performance and possible denial of service.

Record
CVE-2021-41039
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02
Show 4 moreShow less
OSVDEBIAN-CVE-2021-41039 7.5

In versions 1.6 to 2.0.11 of Eclipse Mosquitto, an MQTT v5 client connecting with a large number of user-property properties could cause excessive CPU usage, leading to a loss of performance and possible denial of service.

Record
DEBIAN-CVE-2021-41039
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02
OSVOESA-2022-1498 7.5

mosquitto security update

Mosquitto is an open source message broker that implements the MQ Telemetry Transport protocol version 3.1 and 3.1.1 MQTT provides a lightweight method of carrying out messaging using a publish/subscribe model. This makes it suitable for "machine to machine" messaging such as with low power sensors or mobile devices such as phones, embedded computers or micro-controllers like the Arduino.

Security Fix(es):

In versions 1.6 to 2.0.11 of Eclipse Mosquitto, an MQTT v5 client connecting with a large number of user-property properties could cause excessive CPU usage, leading to a loss of performance and possible denial of service.(CVE-2021-41039)

Record
OESA-2022-1498
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02
OSVUBUNTU-CVE-2021-41039 7.5

In versions 1.6 to 2.0.11 of Eclipse Mosquitto, an MQTT v5 client connecting with a large number of user-property properties could cause excessive CPU usage, leading to a loss of performance and possible denial of service.

Record
UBUNTU-CVE-2021-41039
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02
OSVUSN-6492-1 No score

mosquitto vulnerabilities

Kathrin Kleinhammer discovered that Mosquitto incorrectly handled certain inputs. If a user or an automated system were provided with a specially crafted input, a remote attacker could possibly use this issue to cause a denial of service. This issue only affected Ubuntu 20.04 LTS. (CVE-2021-34431)

Zhanxiang Song discovered that Mosquitto incorrectly handled certain inputs. If a user or an automated system were provided with a specially crafted input, a remote attacker could possibly use this issue to cause an authorisation bypass. This issue only affected Ubuntu 22.04 LTS and Ubuntu 23.04. (CVE-2021-34434)

Zhanxiang Song, Bin Yuan, DeQing Zou, and Hai Jin discovered that Mosquitto incorrectly handled certain inputs. If a user or an automated system were provided with a specially crafted input, a remote attacker could possibly use this issue to cause a denial of service. This issue only affected Ubuntu 20.04 LTS and Ubuntu 22.04 LTS. (CVE-2021-41039)

Zhengjie Du discovered that Mosquitto incorrectly handled certain inputs. If a user or an automated system were provided with a specially crafted input file, a remote attacker could possibly use this issue to cause a denial of service. (CVE-2023-0809)

It was discovered that Mosquitto incorrectly handled certain inputs. If a user or an automated system were provided with a specially crafted input, a remote attacker could possibly use this issue to cause a denial of service. (CVE-2023-3592)

Mischa Bachmann discovered that Mosquitto incorrectly handled certain inputs. If a user or an automated system were provided with a specially crafted input, a remote attacker could possibly use this issue to cause a denial of service. This issue was only fixed in Ubuntu 22.04 LTS and Ubuntu 23.04. (CVE-2023-28366)

Record
USN-6492-1
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
mosquitto
Debian:12
 before 2.0.11-1.2
2.0.11-1.2
mosquitto
Debian:13
 before 2.0.11-1.2
2.0.11-1.2
mosquitto
Debian:14
 before 2.0.11-1.2
2.0.11-1.2
mosquitto
openEuler:20.03-LTS-SP1
 before 1.6.15-5.oe1
1.6.15-5.oe1
mosquitto
openEuler:20.03-LTS-SP2
 before 1.6.15-5.oe1
1.6.15-5.oe1
mosquitto
openEuler:20.03-LTS-SP3
 before 1.6.15-5.oe1
1.6.15-5.oe1
mosquitto
Ubuntu:Pro:20.04:LTS
 before 1.6.9-1ubuntu0.1~esm1, plus listed versions
1.6.6-11.6.7-11.6.8-11.6.8-21.6.9-1~build11.6.9-1
1.6.9-1ubuntu0.1~esm1
mosquitto
Ubuntu:22.04:LTS
 before 2.0.11-1ubuntu1.1, plus listed versions
2.0.11-12.0.11-1build12.0.11-1ubuntu1
2.0.11-1ubuntu1.1
mosquitto
Ubuntu:Pro:20.04:LTS
From an advisory covering 6 CVEs
 before 1.6.9-1ubuntu0.1~esm1, plus listed versions
1.6.6-11.6.7-11.6.8-11.6.8-21.6.9-1~build11.6.9-1
1.6.9-1ubuntu0.1~esm1
mosquitto
Ubuntu:22.04:LTS
From an advisory covering 6 CVEs
 before 2.0.11-1ubuntu1.1, plus listed versions
2.0.11-12.0.11-1build12.0.11-1ubuntu1
2.0.11-1ubuntu1.1

History

History
RecordedChangedSources
affected, facts
aliasesEUVD
first indexedCVE List, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2021-41039 is a high vulnerability (CVSS 7.5) in Eclipse Mosquitto, published December 1, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 1.35%, the 71st percentile. Fixed in mosquitto 2.0.11-1.2.

References

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