Mosquitto
CVE-2021-34434
MEDIUM
Vulnerability Assessment
| Weakness |
CWE
OWASP Top 10:2025
A01:2025 - Broken Access Control
ASVS 5.0
V8 - Authorization Authorization verification
MITRE ATT&CK
1 technique across 1 tactic: Defense Evasion The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up. |
| Impact | CVSS score of 5.3 (MEDIUM). Attack characteristics: network attack vector, low complexity, no privileges required, no user interaction not required. Public proof-of-concept exploit code is available. |
| Exploit ScenarioDerived | This vulnerability can be exploited remotely over the network. Successful exploitation could compromise the medium-severity affected system. |
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Alert meAnalysisAI
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. Rated medium severity (CVSS 5.3), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available and no vendor patch available.
RemediationAI
No vendor patch is available at time of analysis. Monitor vendor advisories for updates. Apply vendor patches when available. Implement network segmentation and monitoring as interim mitigations.
Affects your stack
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Checking this CVE against your own stacks and servers is part of the Basic plan and up.
Technical ContextAI · show details
This vulnerability is classified under CWE-285. 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. Affected products include: Eclipse Mosquitto, Fedoraproject Fedora.
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- Exploit and PoC references, threat intelligence from 22 sources
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Severity by source
AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Primary rating from NVD · only source for this CVE.
CVSS VectorNVD
DescriptionNVD
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.
Threat Intelligence Overview
NVD
CVE.org
EPSS
How this decision was reached
The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.
What every action level means
SSVC AssessmentENISA
Priority Score
Attack Technique
Authentication bypass attacks exploit flaws in the verification mechanisms that control access to systems and applications.
Affected Products (CPE)NVD
In Eclipse Mosquitto versions 2.0.7 and earlier, the server will crash if the client tries to send a PUBLISH packet with
In versions 1.6 to 2.0.11 of Eclipse Mosquitto, an MQTT v5 client connecting with a large number of user-property proper
In Eclipse Mosquitto, from version 1.3.2 through 2.0.18, if a malicious broker sends a crafted SUBACK packet with no rea
In Mosquitto before 1.4.12, pattern based ACLs can be bypassed by clients that set their username/client id to '#' or '+
In Eclipse Mosquito, versions from 2.0.0 through 2.0.18, if a Mosquitto broker is configured to create an outgoing bridg
In Eclipse Mosquito before and including 2.0.5, establishing a connection to the mosquitto server without sending data c
In Mosquitto before 2.0.16, a memory leak occurs when clients send v5 CONNECT packets with a will message that contains
The broker in Eclipse Mosquitto 1.3.2 through 2.x before 2.0.16 has a memory leak that can be abused remotely when a cli
Eclipse Mosquitto 1.5.x before 1.5.5 allows ACL bypass: if the option per_listener_settings was set to true, and the def
In Eclipse Mosquitto versions 1.5 to 1.5.2 inclusive, if a message is published to Mosquitto that has a topic starting w
In Eclipse Mosquitto up to version 2.0.18a, an attacker can achieve memory leaking, segmentation fault or heap-use-after
In Eclipse Mosquitto version 1.6 to 2.0.10, if an authenticated client that had connected with MQTT v5 sent a crafted CO
GitHub PoC
Exploit-DB