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Vulnerability record · CVE-2021-34434 · published 30 August 2021

CVE-2021-34434: Eclipse mosquitto improper authorization vulnerability

Eclipse · Mosquitto

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.

5.3 CVSS 3.1 Medium EPSS 1.3% · top 30.1% CWE-285 · Improper authorizationCWE-863 · Incorrect authorization
5.3CVSS 3.1 base score, v2 5.0
1.3%EPSS exploitation probability, 30 days
NoNot in CISA KEV
2Affected product versions listed by NVD
8References, 2 tagged exploit
17 Jun 2026Last modified by NVD

Description

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.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

Affected products

2 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://bugs.eclipse.org/bugs/show_bug.cgi?id=575324 ExploitIssue TrackingVendor Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/K4WWGVF5BUFPYPCFUPPP4KR
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/RLUUM52Y6AEICPXPSRRXC6O
https://www.debian.org/security/2023/dsa-5511
https://bugs.eclipse.org/bugs/show_bug.cgi?id=575324 ExploitIssue TrackingVendor Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/K4WWGVF5BUFPYPCFUPPP4KR
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/RLUUM52Y6AEICPXPSRRXC6O
https://www.debian.org/security/2023/dsa-5511

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Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2021-34434), CISA KEV, FIRST EPSS (scores of 2026-09-28). This page is refreshed as NVD updates the record.