CVE-2018-12543
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedIn 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.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceIn Eclipse Mosquitto versions 1.5 through 1.5.2, an assertion can be triggered when a message is published to a topic beginning with $ but not matching the $SYS namespace (e.g., $test/test), causing the broker to exit unexpectedly. This results in a denial of service condition.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data>= 1.5.0, <= 1.5.2CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify installed Mosquitto versionRun 'mosquitto -h' or 'mosquitto --version' to display the version number, or check the package manager for the installed version.Affected if The version is 1.5.0, 1.5.1, or 1.5.2.
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Verify broker is running and accessibleConfirm the Mosquitto broker process is active and accepting connections. Use 'ps aux | grep mosquitto' or check if the default port 1883 is listening with 'netstat -an | grep 1883'.Affected if The broker is running and reachable on the network.
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Check for anonymous or unauthenticated accessExamine the Mosquitto configuration file (mosquitto.conf) for 'allow_anonymous true' or verify that no authentication mechanism is enforced.Affected if Anonymous access is permitted, allowing any client to publish to topics.
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Inspect access control rules for $ topicsReview ACL definitions in mosquitto.conf or any included ACL files. Look for patterns that allow wildcards or specific grants for topics beginning with $.Affected if ACLs permit publishing to topics like $test/test or other $-prefixed topics that are not $SYS.
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Identify active non-$SYS $ topicsMonitor or query for any existing subscriptions or published messages on topics that start with $ but are not in the $SYS namespace, such as $test or $user/data.Affected if There are active publishers or subscribers using $-prefixed topics that are not $SYS.
You are affected if Mosquitto version 1.5.0-1.5.2 is running and clients can publish to any topic starting with $ that is not part of the $SYS namespace, causing an assertion failure and broker exit.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor dataUpgrade Eclipse Mosquitto to version 1.5.3 or later, which contains the fix for this assertion handling. If immediate upgrade is not possible, implement access controls to prevent unauthenticated or unauthorized users from publishing to topics starting with $.
- Consultation2.0 h
- Implementation3.0 h
- Testing2.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2018-12543 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2018-12543 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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