What is CVE-2018-12543?

CVE-2018-12543 is a high-severity vulnerability in Eclipse Mosquitto, classified under Reachable Assertion. CVSS score: 7.5/10. Published 2018-11-15.

How severe is CVE-2018-12543?

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

Is CVE-2018-12543 known to be exploited?

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

Improper input validation in Eclipse Mosquitto

CVE-2018-12543

In Eclipse Mosquitto versions 1.5 to 1.5.2 inclusive, if a message is published to Mosquitto that has a topic starting with $, but that is not $SYS, e.g. $test/test, then an assert is triggered that should otherwise not be reachable and Mosquitto will exit.

Published 2018-11-15 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.360 (98.4th percentile), scored 2026-09-28.

Moderate probability of exploitation in the next 30 days — watch for active exploitation reports. 98th percentile — 98.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.360 · newest: 0.360 · change: 0.000

Affected products

Eclipse Mosquitto
The Eclipse Foundation Mosquitto — versions unspecified, 1.5

Weakness classification (CWE)

Public proof-of-concept exploits

References

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

Frequently asked questions

What is CVE-2018-12543?: CVE-2018-12543 is a high-severity vulnerability in Eclipse Mosquitto, classified under Reachable Assertion. CVSS score: 7.5/10. Published 2018-11-15.
How severe is CVE-2018-12543?: High severity. CVSS v3 base score is 7.5 out of 10.
Is CVE-2018-12543 known to be exploited?: 2 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.