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CVE-2021-34434

In Eclipse Mosquitto versions 2.0 to 2.0.11, when using the dynamic security plugin, if the...

5.3 MediumFix available

In Eclipse Mosquitto versions 2.0 to 2.0.11, when using the dynamic security plugin, if the ability for a client to make subscriptions on a topic is revoked when a durable client is offline, then existing subscriptions for that client are not revoked.

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
Low
Integrity
None
Availability
None

Exploit likelihood

1.33%Up 0.9 points since Aug 31, 2021
90%50%10%1%

What each source reports

NVD Score used 5.3

In Eclipse Mosquitto versions 2.0 to 2.0.11, when using the dynamic security plugin, if the ability for a client to make subscriptions on a topic is revoked when a durable client is offline, then existing subscriptions for that client are not revoked.

Record
CVE-2021-34434
CVSS 3.1
5.3 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
CVSS 2.0
5.0 MediumAV:N/AC:L/Au:N/C:P/I:N/A:N
Weakness
CWE-285, CWE-863
Updated
2026-11-02
CVE List No score

In Eclipse Mosquitto versions 2.0 to 2.0.11, when using the dynamic security plugin, if the ability for a client to make subscriptions on a topic is revoked when a durable client is offline, then existing subscriptions for that client are not revoked.

Record
CVE-2021-34434
Weakness
CWE-285
Updated
2026-11-02
EUVDEUVD-2021-21090 No score

In Eclipse Mosquitto versions 2.0 to 2.0.11, when using the dynamic security plugin, if the ability for a client to make subscriptions on a topic is revoked when a durable client is offline, then existing subscriptions for that client are not revoked.

Record
EUVD-2021-21090
Updated
2026-11-03
GitHub AdvisoriesGHSA-cj6r-mprf-8cq9 5.3

In Eclipse Mosquitto versions 2.0 to 2.0.11, when using the dynamic security plugin, if the...

In Eclipse Mosquitto versions 2.0 to 2.0.11, when using the dynamic security plugin, if the ability for a client to make subscriptions on a topic is revoked when a durable client is offline, then existing subscriptions for that client are not revoked.

Record
GHSA-cj6r-mprf-8cq9
CVSS 3.1
5.3 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Weakness
CWE-285, CWE-863
Updated
2026-11-02
OSVBELL-CVE-2021-34434 5.3

CVE-2021-34434 does not affect BellSoft software

Record
BELL-CVE-2021-34434
CVSS 3.1
5.3 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Updated
2026-11-02
OSV 5.3

In Eclipse Mosquitto versions 2.0 to 2.0.11, when using the dynamic security plugin, if the ability for a client to make subscriptions on a topic is revoked when a durable client is offline, then existing subscriptions for that client are not revoked.

Record
CVE-2021-34434
CVSS 3.1
5.3 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Updated
2026-11-02
Show 5 moreShow less
OSVDEBIAN-CVE-2021-34434 5.3

In Eclipse Mosquitto versions 2.0 to 2.0.11, when using the dynamic security plugin, if the ability for a client to make subscriptions on a topic is revoked when a durable client is offline, then existing subscriptions for that client are not revoked.

Record
DEBIAN-CVE-2021-34434
CVSS 3.1
5.3 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Updated
2026-11-02
OSVUBUNTU-CVE-2021-34434 5.3

In Eclipse Mosquitto versions 2.0 to 2.0.11, when using the dynamic security plugin, if the ability for a client to make subscriptions on a topic is revoked when a durable client is offline, then existing subscriptions for that client are not revoked.

Record
UBUNTU-CVE-2021-34434
CVSS 3.1
5.3 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Updated
2026-11-02
OSVMGASA-2021-0445 No score

Updated mosquitto packages fix security vulnerability

Mosquitto is updated to 2.0.12 to fix security vulnerability:

In Eclipse Mosquitto versions 2.0 to 2.0.11, when using the dynamic security plugin, if the ability for a client to make subscriptions on a topic is revoked when a durable client is offline, then existing subscriptions for that client are not revoked (CVE-2021-34434).

Record
MGASA-2021-0445
Updated
2026-11-02
OSVopenSUSE-SU-2024:11575-1 No score

libmosquitto1-2.0.12-1.1 on GA media

These are all security issues fixed in the libmosquitto1-2.0.12-1.1 package on the GA media of openSUSE Tumbleweed.

Record
openSUSE-SU-2024:11575-1
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+deb12u1, plus listed versions
2.0.11-1.2
2.0.11-1.2+deb12u1
mosquitto
Debian:13
 before 2.0.15-1
2.0.15-1
mosquitto
Debian:14
 before 2.0.15-1
2.0.15-1
mosquitto
Debian:11
From an advisory covering 4 CVEs
 before 2.0.11-1+deb11u1, plus listed versions
2.0.11-1
2.0.11-1+deb11u1
mosquitto
Debian:12
From an advisory covering 4 CVEs
 before 2.0.11-1.2+deb12u1, plus listed versions
2.0.11-1.2
2.0.11-1.2+deb12u1
mosquitto
Mageia:8
 before 2.0.12-1.mga8
2.0.12-1.mga8
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-2021-34434 is a medium vulnerability (CVSS 5.3) in Eclipse Mosquitto, published August 30, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 1.33%, the 71st percentile. Fixed in mosquitto 2.0.11-1.2+deb12u1.

References

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