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Out-of-bounds ReadWeakness · CWE-125

CVE-2026-54412

HIGH · 8.2 CVSS v3.1 Published 2026-06-14
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
91/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

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 · unedited
LiamBindle MQTT-C through version 1.1.6 contains a heap-based out-of-bounds read and integer underflow in the mqtt_unpack_publish_response function in src/mqtt.c that allows a remote unauthenticated attacker controlling an MQTT broker - or able to inject MQTT traffic into an unencrypted session - to crash a subscribed MQTT-C client and potentially disclose adjacent heap memory by sending a single crafted PUBLISH packet.

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 confidence

MQTT-C library versions through 1.1.6 have a heap-based out-of-bounds read and integer underflow vulnerability in the mqtt_unpack_publish_response function in src/mqtt.c. A remote attacker controlling a malicious MQTT broker or able to inject traffic into an unencrypted session can send a single crafted PUBLISH packet to trigger the integer underflow, causing the client to crash and potentially leaking adjacent heap memory to the attacker.

MitigationUpgrade MQTT-C to a version beyond 1.1.6 that patches the mqtt_unpack_publish_response function with proper bounds validation and integer overflow/underflow checks before processing PUBLISH packet response data.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS 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
Low
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/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 checks

Work through these to decide whether this CVE applies to you.

  1. Identify MQTT-C library usage
    Search project files for '#include "mqtt.h"' or check build system for libmqtt linkage (CMake, Makefile, package config)
    Affected if MQTT-C library is linked or included in the project
  2. Determine MQTT-C version
    Check library version in build artifacts, git submodule, or package manager (e.g., 'grep -r "1.1.6"' in source, or 'mqtt.h' for version macros)
    Affected if Version is 1.1.6 or earlier (any version through 1.1.6 is affected)
  3. Verify use of mqtt_unpack_publish_response
    Search source code for calls to mqtt_unpack_publish_response() function, typically in MQTT PUBLISH packet handling code
    Affected if Application code calls mqtt_unpack_publish_response to process incoming PUBLISH packets
  4. Confirm PUBLISH packet processing is enabled
    Review application code to confirm it processes incoming MQTT PUBLISH messages from clients (subscribe/publish pattern)
    Affected if Application receives and parses MQTT PUBLISH packets from network sources

You are affected if your application uses MQTT-C version 1.1.6 or earlier and processes incoming MQTT PUBLISH packets via mqtt_unpack_publish_response().

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade MQTT-C to a version beyond 1.1.6 that patches the mqtt_unpack_publish_response function with proper bounds validation and integer overflow/underflow checks before processing PUBLISH packet response data.

Recommended fix Moderate confidence

Latest stable release of MQTT-C (version > 1.1.6)

  1. 1. Identify the current MQTT-C version in use by checking your project dependencies (e.g., in package.json, requirements.txt, or submodule references)
  2. 2. Navigate to the MQTT-C GitHub repository at github.com/LiamBindle/MQTT-C
  3. 3. Review the releases section to identify the latest stable release version
  4. 4. Update your dependency to use the latest available version of MQTT-C
  5. 5. Rebuild and test your application to ensure the library functions correctly with the new version
  6. 6. Verify that the mqtt_unpack_publish_response() function now properly validates topic_name_size against remaining_length before use
Caveat Minor: Review release notes for any API changes between 1.1.6 and the target version; unlikely to have breaking changes for patch releases

Generated from the published advisory — verify against the referenced sources before acting.

Have this fixed Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
11.0 hours of engineering $1,930
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-54412 in production — separate from our analysis above.

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What this is

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.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
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  • No spam, self-promotion, credentials, or personal data