Ubuntu LinuxOperating system · Canonical
CVE-2019-11779
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 1.5.0 to 1.6.5 inclusive, if a malicious MQTT client sends a SUBSCRIBE packet containing a topic that consists of approximately 65400 or more '/' characters, i.e. the topic hierarchy separator, then a stack overflow will occur.
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 confidenceA stack overflow vulnerability exists in Eclipse Mosquitto MQTT broker versions 1.5.0 through 1.6.5. When a malicious client sends a SUBSCRIBE packet containing a topic with approximately 65400 or more '/' (hierarchy separator) characters, a stack overflow occurs, causing the broker to crash. This results in denial of service for all connected clients.
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
Ubuntu LinuxOperating system
= 19.04
FedoraOperating system
= 29= 30= 31
Debian LinuxOperating system
= 8.0= 10.0>= 1.5, < 1.5.9>= 1.6, < 1.6.6= 15.0= 15.1CVSS 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
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:L/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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Check if Mosquitto is installedOn Debian/Ubuntu: dpkg -l | grep mosquitto. On Fedora/RHEL: rpm -qa | grep mosquitto. On openSUSE: rpm -qa | grep mosquitto.Affected if No Mosquitto package is found, the system is not affected.
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Determine installed Mosquitto versionRun mosquitto --help or mosquitto -h and look for version output. Alternatively, check the package version from the package manager output from step 1.Affected if The version is 1.5.0 through 1.5.8, or 1.6.0 through 1.6.5.
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Verify Mosquitto service is runningRun systemctl status mosquitto or ps aux | grep mosquitto to check if the broker process is active.Affected if Mosquitto is not running, the vulnerability cannot be exploited.
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Check if MQTT port is accessible from untrusted networksReview firewall rules (iptables -L or firewall-cmd --list-all) and network configuration to determine if port 1883 (default MQTT) is exposed to external clients.Affected if Port 1883 is accessible to untrusted network segments, the broker is remotely exploitable.
You are affected if Mosquitto version 1.5.0-1.5.8 or 1.6.0-1.6.5 is running and accessible, and a remote client can send SUBSCRIBE packets to the broker.
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 data1.5.91.6.6
Upgrade Eclipse Mosquitto to version 1.6.6 or later. If immediate upgrade is not feasible, consider implementing network-level input validation or rate limiting on SUBSCRIBE packets to block abnormally long topic strings.
Fix this in Ubuntu Linux
Scoped from the published advisory
- Consultation2.0 h
- Implementation4.0 h
- Testing4.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,328.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2019-11779 — 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-2019-11779 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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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
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