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Fencer Vulns
medium 5.3

CVE-2021-34434 json

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…

published 2021-08-30 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-21090

cvss
5.3
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
1.3%
EPSS 1.3% chance of exploitation in 30 days, percentile 71%
public exploits
0
none known

Summary

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.

Patch / fix

  • mosquitto Debian 12 2.0.11-1.2+deb12u1
  • mosquitto Debian 14, Debian 13 2.0.15-1

debian advisories DEBIAN-CVE-2021-34434

  • mosquitto Ubuntu 22.04 LTS 2.0.11-1ubuntu1.1

ubuntu advisories UBUNTU-CVE-2021-34434

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • mosquitto Arch Linux 2.0.12-1

arch linux advisories AVG-2332

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2021-34434 updated cvss 6.8

mosquitto: Existing subscriptions for that client are not revoked

  • Red Hat All currently supported Red Hat products
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

1.33% chance of exploitation in the next 30 days, higher than 71% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • bugs.eclipse.org https://bugs.eclipse.org/bugs/show_bug.cgi?id=575324 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
NVD 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
NVD 2.0 5.0 AV:N/AC:L/Au:N/C:P/I:N/A:N

Affected products

  • The Eclipse Foundation Eclipse Mosquitto

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.