dbcve.org
Paho MqttApplication · Eclipse

CVE-2025-10543

MEDIUM · 5.3 CVSS v3.1 Published 2025-12-02
Fix available
A fix is available. Upgrade to after 1.5.0 or later.
See remediation →
62/100
Remediation priority · Elevated
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
In Eclipse Paho Go MQTT v3.1 library (paho.mqtt.golang) versions <=1.5.0 UTF-8 encoded strings, passed into the library, may be incorrectly encoded if their length exceeds 65535 bytes. This may lead to unexpected content in packets sent to the server (for example, part of an MQTT topic may leak into the message body in a PUBLISH packet). The issue arises because the length of the data passed in was converted from an int64/int32 (depending upon CPU) to an int16 without checks for overflows. The int16 length was then written, followed by the data (e.g. topic). This meant that when the data (e.g. topic) was over 65535 bytes then the amount of data written exceeds what the length field indicates. This could lead to a corrupt packet, or mean that the excess data leaks into another field (e.g. topic leaks into message body).

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 · moderate confidence

The Eclipse Paho Go MQTT library versions <=1.5.0 contains an integer truncation vulnerability where UTF-8 strings (such as topic names or message payloads) exceeding 65535 bytes have their length converted from int64/int32 to int16 without overflow validation. This causes the packet length field to be incorrect, potentially leaking excess data (e.g., topic name) into subsequent packet fields like the message body in PUBLISH packets.

MitigationUpgrade to a patched version >1.5.0 when available, or implement application-layer validation to reject or split input strings exceeding 65535 bytes before passing them to the library.

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
Paho MqttApplication
Affected:<= 1.5.0

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
None

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

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 Eclipse Paho Go MQTT library version
    Check your go.mod file for 'github.com/eclipse/paho.mqtt.golang' and its version, or run 'go list -m github.com/eclipse/paho.mqtt.golang' in your project directory
    Affected if The version listed is 1.5.0 or lower
  2. Confirm Go module usage
    Verify that your application imports and uses the paho.mqtt.golang library, typically found in import statements containing 'paho.mqtt.golang'
    Affected if Your codebase imports and uses this library for MQTT communications
  3. Identify UTF-8 string handling paths
    Search your codebase for Publish calls or topic subscription operations where topic names or message payloads could be set or constructed at runtime
    Affected if Your application processes topic names or message payloads that could exceed 65535 bytes in length
  4. Review packet construction logic
    Inspect how the library handles packet encoding, particularly in Publish packet creation where the remaining length field is calculated from string lengths
    Affected if Your MQTT client handles large payloads or topics without application-layer length validation before passing them to the library

You are affected if you use Eclipse Paho Go MQTT library version 1.5.0 or lower and your application processes topic names or message payloads that can exceed 65535 bytes, causing potential data leakage into subsequent packet fields.

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
Upgrade available Upgrade to a release after 1.5.0
Interim mitigation

Upgrade to a patched version >1.5.0 when available, or implement application-layer validation to reject or split input strings exceeding 65535 bytes before passing them to the library.

Recommended fix Moderate confidence

1.5.1 or later (check GitLab Eclipse for exact stable release)

  1. 1. Identify all Go projects using paho.mqtt.golang version 1.5.0 or earlier
  2. 2. Update the dependency to the latest version using: go get github.com/eclipse/paho.mqtt.golang@latest
  3. 3. Run go mod tidy to update go.mod and go.sum files
  4. 4. Rebuild and test all applications that depend on this library
  5. 5. Verify that MQTT packets are correctly encoded for topics and payloads of any length
Caveat Review release notes for potential behavioral changes in 1.5.1+; test thoroughly with large topic/payload sizes

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

Fix this in Paho Mqtt Scoped from the published advisory
  • Consultation4.0 h
  • Implementation4.0 h
  • Testing8.0 h
  • Review / QA4.0 h
20.0 hours of engineering $3,440
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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-2025-10543 in production — separate from our analysis above.

No notes yet

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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
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data