CVE-2025-10543

paho.mqtt.golang: paho.mqtt.golang: Integer Overflow in UTF-8 String Encoding

Published Dec 2, 2025 CVSS 4.0 · 6.3 Medium EPSS < 1% KEV · Not listed
Description
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).

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Github GHSA Github GHSA GHSA-32fw-gq77-f2f2 Eclipse Paho Go MQTT may incorrectly encode strings if length exceeds 65535 bytes
History
Type Values Removed Values Added
First Time appeared Eclipse paho Mqtt
CPEs cpe:2.3:a:eclipse:paho_mqtt:*:*:*:*:*:go:*:*
Vendors & Products Eclipse paho Mqtt
Metrics cvssV3_1

{'score': 6.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N'}

cvssV3_1

{'score': 5.3, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N'}

Type Values Removed Values Added
Title paho.mqtt.golang: paho.mqtt.golang: Integer Overflow in UTF-8 String Encoding
References
Metrics threat_severity

None

cvssV3_1

{'score': 6.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N'}

threat_severity

Moderate

Type Values Removed Values Added
First Time appeared Eclipse
Eclipse paho Go Mqtt
Vendors & Products Eclipse
Eclipse paho Go Mqtt
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
Description 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).
Weaknesses CWE-197
CWE-681
References
Metrics cvssV4_0

{'score': 6.3, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
eclipse
Published
Updated
Dec 2, 2025, 1:55 PM
Reserved
Sep 16, 2025, 7:59 AM
Status
Analyzed
Published
Dec 2, 2025, 9:15 AM
Modified
Oct 18, 2026, 6:10 PM
Severity
Moderate
Public date
Dec 2, 2025, 8:18 AM