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.

published 2021-07-27 5 y ago modified 2026-07-02 4 mo ago also EUVD-2021-21088

cvss: 7.5; version 3.1, NVD
cisa kev: Not listed; not in CISA's catalog
epss: 1.2%; EPSS 1.2% chance of exploitation in 30 days, percentile 69%
public exploits: 0; none known

Patch / fix

distros 2 links 1

debian alpine

mosquitto Debian 14, Debian 13, Debian 12 2.0.8-1

debian advisories DEBIAN-CVE-2021-34432

mosquitto Alpine 3.11 1.6.8-r1
mosquitto Alpine 3.12 1.6.9-r1
mosquitto Alpine 3.13 1.6.12-r3
mosquitto Alpine 3.24, Alpine 3.23, Alpine 3.22 +8 more 2.0.8-r0

alpine advisories ALPINE-CVE-2021-34432

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

bugs.eclipse.org/bugs/show_bug.cgi?id=574141 advisory

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-2021-34432 updated 2026-07-02 cvss 7.5

mosquitto: DoS when client tries to send a PUBLISH packet with topic length = 0

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

1.25% chance of exploitation in the next 30 days, higher than 69% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

bugs.eclipse.org https://bugs.eclipse.org/bugs/show_bug.cgi?id=574141 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
NVD	3.1	7.5	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD	2.0	5.0	AV:N/AC:L/Au:N/C:N/I:N/A:P

Affected products

The Eclipse Foundation Eclipse Mosquitto

Classification

Weakness

CWE-20 Improper Input Validation

References

bugs.eclipse.org /bugs/show_bug.cgi?id=574141
exploit, issue-tracking, patch, vendor-advisory

Sources

CVE List CVE-2021-34432
NVD CVE-2021-34432

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.

Summary