CVE-2019-17210
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 · uneditedA denial-of-service issue was discovered in the MQTT library in Arm Mbed OS 2017-11-02. The function readMQTTLenString() is called by the function MQTTDeserialize_publish() to get the length and content of the MQTT topic name. In the function readMQTTLenString(), mqttstring->lenstring.len is a part of user input, which can be manipulated. An attacker can simply change it to a larger value to invalidate the if statement so that the statements inside the if statement are skipped, letting the value of mqttstring->lenstring.data default to zero. Later, curn is accessed, which points to mqttstring->lenstring.data. On an Arm Cortex-M chip, the value at address 0x0 is actually the initialization value for the MSP register. It is highly dependent on the actual firmware. Therefore, the behavior of the program is unpredictable from this time on.
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 denial-of-service vulnerability in Arm Mbed OS MQTT library allows attackers to manipulate the len field in readMQTTLenString(), causing the data pointer to default to zero. When the code later dereferences this null pointer on Arm Cortex-M devices, it reads from address 0x0 (the MSP register initialization value), causing unpredictable program behavior.
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= 2017-11-02all versionsCVSS 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:3.1/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.
-
Identify MQTT library versionLocate the Mbed MQTT library in your project dependencies (typically in mbedtls or a separate mqtt folder). Check the version metadata or commit hash. The affected version is specifically the 2017-11-02 release.Affected if The MQTT library version matches exactly 2017-11-02
-
Confirm Arm Mbed OS usageVerify your project compiles against Arm Mbed OS (check makefile, CMakeLists.txt, or mbed_app.json for mbed-os dependency).Affected if Your application runs on Arm Mbed OS with the MQTT library included
-
Check for MQTT publish deserializationSearch your codebase for calls to MQTTDeserialize_publish() function. This function deserializes incoming MQTT publish packets and calls readMQTTLenString() internally.Affected if Your code processes incoming MQTT publish messages using MQTTDeserialize_publish
-
Inspect readMQTTLenString usageReview the MQTT packet parsing code in your build. The vulnerability exists when readMQTTLenString() processes the len field from network input without bounds validation.Affected if Your MQTT implementation reads variable-length strings from network packets without validating length fields exceed buffer bounds
-
Verify Cortex-M deployment targetConfirm the target hardware is an Arm Cortex-M processor (e.g., STM32, NXP LPC, Kinetis, Nordic nRF52). This matters because only Cortex-M reads 0x0 as the initial MSP value.Affected if The firmware runs on an Arm Cortex-M based microcontroller
You are affected if your firmware uses Arm Mbed OS with the MQTT library version 2017-11-02 and processes MQTT publish messages on Cortex-M hardware, allowing a crafted packet to cause a null pointer dereference at address 0x0.
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 dataImplement proper bounds checking and null pointer validation on the length and data pointer in readMQTTLenString() before dereferencing; ensure MQTTDeserialize_publish() validates all user-controlled inputs before use.
- Consultation4.0 h
- Implementation8.0 h
- Testing6.0 h
- Review / QA4.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $6,176.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2019-17210 — 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-2019-17210 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
Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.
A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.
- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
- No spam, self-promotion, credentials, or personal data