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.
CVSS 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
CVSS Score: 7.8
A malicious MQTT broker, or a network attacker capable of injecting a single MQTT PUBLISH packet into an unencrypted session that the victim client has subscribed to, sends one crafted packet with topic_name_size = 0xFFFF and remaining_length = 7 to crash an MQTT-C-based client process and optionally disclose adjacent heap bytes through the out-of-bounds read primitive.
| Exploitability Metrics |
Vulnerable System Impact Metrics |
Subsequent System Impact Metrics |
| Attack Vector |
Network |
Confidentiality |
Low |
Confidentiality |
None |
| Attack Complexity |
Low |
Integrity |
None |
Integrity |
None |
| Attack Requirements |
None |
Availability |
High |
Availability |
None |
| Privileges Required |
None |
| User Interaction |
None |
A malicious MQTT broker, or a network attacker capable of injecting a single MQTT PUBLISH packet into an unencrypted session that the victim client has subscribed to, sends one crafted packet with topic_name_size = 0xFFFF and remaining_length = 7 to crash an MQTT-C-based client process and optionally disclose adjacent heap bytes through the out-of-bounds read primitive.
CVSS 4.0