What is CVE-2021-34432?

CVE-2021-34432 is a high-severity vulnerability in Eclipse Mosquitto, classified under Improper Input Validation. CVSS score: 7.5/10. Published 2021-07-27.

How severe is CVE-2021-34432?

High severity. CVSS v3 base score is 7.5 out of 10.

Is CVE-2021-34432 known to be exploited?

3 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.

Improper input validation in Eclipse Mosquitto

CVE-2021-34432

In Eclipse Mosquitto versions 2.0.7 and earlier, the server will crash if the client tries to send a PUBLISH packet with topic length = 0.

Vulnerability class: Drupalgeddon 2 (CVE-2018-7600)

Published 2021-07-27 · last modified 2026-07-02.

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.012 (68.1th percentile), scored 2026-09-29.

Low probability of exploitation in the next 30 days, but still tracked. 68th percentile — 68.1% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.012 · newest: 0.012 · change: 0.000

Affected products

Eclipse Mosquitto
The Eclipse Foundation Mosquitto — versions unspecified

Weakness classification (CWE)

CWE-20 — Improper Input Validation

Public proof-of-concept exploits

References

bugs.eclipse.org/bugs/show_bug.cgi (Exploit, Patch, Issue Tracking, Vendor Advisory)

Frequently asked questions

What is CVE-2021-34432?: CVE-2021-34432 is a high-severity vulnerability in Eclipse Mosquitto, classified under Improper Input Validation. CVSS score: 7.5/10. Published 2021-07-27.
How severe is CVE-2021-34432?: High severity. CVSS v3 base score is 7.5 out of 10.
Is CVE-2021-34432 known to be exploited?: 3 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.