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Vulnerability record · CVE-2018-12551 · published 27 March 2019

CVE-2018-12551: Eclipse mosquitto improper authentication vulnerability

Eclipse · Mosquitto

When Eclipse Mosquitto version 1.0 to 1.5.5 (inclusive) is configured to use a password file for authentication, any malformed data in the password file will be treated as valid. This typically means that the malformed data becomes a username and no password. If this occurs, clients can circumvent authentication and get access to the broker by using the malformed username. In particular, a blank line will be treated as a valid empty username. Other security measures are unaffected. Users who have only used the mosquitto_passwd utility to create and modify their password files are unaffected by this vulnerability.

8.1 CVSS 3.0 High EPSS 1.5% · top 27.2% CWE-703 · CWE-703CWE-287 · Improper authentication
8.1CVSS 3.0 base score, v2 6.8
1.5%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
4References, 2 tagged exploit
17 Jun 2026Last modified by NVD

Description

When Eclipse Mosquitto version 1.0 to 1.5.5 (inclusive) is configured to use a password file for authentication, any malformed data in the password file will be treated as valid. This typically means that the malformed data becomes a username and no password. If this occurs, clients can circumvent authentication and get access to the broker by using the malformed username. In particular, a blank line will be treated as a valid empty username. Other security measures are unaffected. Users who have only used the mosquitto_passwd utility to create and modify their password files are unaffected by this vulnerability.

CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected products

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

References

LinkTags
https://bugs.eclipse.org/bugs/show_bug.cgi?id=543401 ExploitIssue TrackingVendor Advisory
https://lists.debian.org/debian-lts-announce/2019/10/msg00035.html
https://bugs.eclipse.org/bugs/show_bug.cgi?id=543401 ExploitIssue TrackingVendor Advisory
https://lists.debian.org/debian-lts-announce/2019/10/msg00035.html

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Related vulnerabilities

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

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Source: NIST National Vulnerability Database (record CVE-2018-12551), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.