CVE-2026-54412

MQTT-C Heap Out-of-Bounds Read and Integer Underflow in mqtt_unpack_publish_response()

Published Jun 14, 2026 CVSS 4.0 · 7.8 High EPSS < 1% KEV · Not listed

Description

LiamBindle MQTT-C versions prior to 1.1.7 contain a heap-based out-of-bounds read and integer underflow in the mqtt_unpack_publish_response() function in src/mqtt.c. A remote unauthenticated attacker controlling an MQTT broker, or capable of injecting MQTT traffic into an unencrypted session, can crash a subscribed MQTT-C client and potentially disclose adjacent heap memory by sending a single crafted PUBLISH packet.

Affected Products

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions

LiamBindle

MQTT-C

unknown

Version	Status	Constraints
`0`	affected	< 1.1.7
`1.1.7`	unaffected	—

No data.

Vendor Product Versions

Liambindle

Mqtt-c

Version	Status	Scheme	Platform
`[0,1.1.6]`	affected	semver	—

Remediation

No solution or workaround provided in the CVE record

Tracking

Advisories

No advisories available

Metrics

Attack Vector Network

Attack Complexity Low

Privileges Required None

Attack Requirements None

User Interaction None

Vulnerable System Confidentiality Impact Low

Vulnerable System Integrity Impact None

Vulnerable System Availability Impact High

Subsequent System Confidentiality Impact None

Subsequent System Integrity Impact None

Subsequent System Availability Impact None

Attack Vector Network

Attack Complexity Low

Privileges Required None

Scope Unchanged

Confidentiality Impact Low

Integrity Impact None

Availability Impact High

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

Exploit prediction score: < 1% (0.430% probability within 30 days)

Exploitation none

Automatable yes

Technical Impact partial

References

Link	Providers
https://cwe.mitre.org/data/definitions/125.html
https://cwe.mitre.org/data/definitions/191.html
https://github.com/LiamBindle/MQTT-C
https://github.com/LiamBindle/MQTT-C/blob/v1.1.6/src/mqtt.c#L1334
https://github.com/LiamBindle/MQTT-C/pull/208
https://github.com/LiamBindle/MQTT-C/releases/tag/v1.1.7

History

Nov 5, 2026 1:00 PM Description updated. Added references View changes

Type	Values Removed	Values Added
Description	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.	LiamBindle MQTT-C versions prior to 1.1.7 contain a heap-based out-of-bounds read and integer underflow in the mqtt_unpack_publish_response() function in src/mqtt.c. A remote unauthenticated attacker controlling an MQTT broker, or capable of injecting MQTT traffic into an unencrypted session, can crash a subscribed MQTT-C client and potentially disclose adjacent heap memory by sending a single crafted PUBLISH packet.
References		https://github.com/LiamBindle/MQTT-C/pull/208 https://github.com/LiamBindle/MQTT-C/releases/tag/v1.1.7

Aug 10, 2026 12:00 PM Description updated. Title updated View changes

Type	Values Removed	Values Added
Description	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. The function validates only that the fixed-header remaining_length is at least 4, then reads the 16-bit topic_name_size field from the broker-controlled packet and advances the parse pointer by that value without verifying that topic_name_size plus the surrounding overhead fits within remaining_length; it subsequently computes application_message_size as remaining_length - topic_name_size - 2 (QoS 0) or - 4 (QoS greater than 0) in unsigned arithmetic, producing an integer underflow that is then passed to memmove(). A PUBLISH packet with topic_name_size = 0xFFFF and remaining_length = 7 advances the parse pointer 65535 bytes past the receive buffer (out-of-bounds read) and causes an application_message_size near 2^32, crashing the process when the resulting memmove() is executed.	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.
Title	MQTT-C - Heap Out-of-Bounds Read and Integer Underflow in mqtt_unpack_publish_response()	MQTT-C Heap Out-of-Bounds Read and Integer Underflow in mqtt_unpack_publish_response()

Aug 10, 2026 11:45 AM Title updated View changes

Type	Values Removed	Values Added
Title	MQTT-C Heap Out-of-Bounds Read and Integer Underflow in mqtt_unpack_publish_response()	MQTT-C - Heap Out-of-Bounds Read and Integer Underflow in mqtt_unpack_publish_response()

Aug 5, 2026 1:45 PM Title updated View changes

Type	Values Removed	Values Added
Title		MQTT-C Heap Out-of-Bounds Read and Integer Underflow in mqtt_unpack_publish_response()

Jun 23, 2026 9:30 PM First appearance in the feed. Affected vendors updated View changes

Type	Values Removed	Values Added
First Time appeared		Liambindle Liambindle mqtt-c
Vendors & Products		Liambindle Liambindle mqtt-c

Jun 15, 2026 5:30 PM Scoring metrics updated View changes

Type	Values Removed	Values Added
Metrics		ssvc `{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}`

Jun 14, 2026 6:00 PM Description updated. Weaknesses updated. Added references. Scoring metrics updated View changes

Type	Values Removed	Values Added
Description		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. The function validates only that the fixed-header remaining_length is at least 4, then reads the 16-bit topic_name_size field from the broker-controlled packet and advances the parse pointer by that value without verifying that topic_name_size plus the surrounding overhead fits within remaining_length; it subsequently computes application_message_size as remaining_length - topic_name_size - 2 (QoS 0) or - 4 (QoS greater than 0) in unsigned arithmetic, producing an integer underflow that is then passed to memmove(). A PUBLISH packet with topic_name_size = 0xFFFF and remaining_length = 7 advances the parse pointer 65535 bytes past the receive buffer (out-of-bounds read) and causes an application_message_size near 2^32, crashing the process when the resulting memmove() is executed.
Weaknesses		CWE-125 CWE-191
References		https://cwe.mitre.org/data/definitions/125.html https://cwe.mitre.org/data/definitions/191.html https://github.com/LiamBindle/MQTT-C https://github.com/LiamBindle/MQTT-C/blob/v1.1.6/src/mqtt.c#L1334
Metrics		cvssV3_1 `{'score': 8.2, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H'}` cvssV4_0 `{'score': 7.8, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:H/SC:N/SI:N/SA:N/E:P/AU:Y/V:D'}`