NanoMQ up to 0.24.13 MQTT Parser mqtt_parser.c nmq_subinfo_decode heap-based overflow

Summaryinfo

A vulnerability has been found in NanoMQ up to 0.24.13 and classified as critical. Affected by this vulnerability is the function nmq_subinfo_decode of the file nng/src/sp/protocol/mqtt/mqtt_parser.c of the component MQTT Parser. The manipulation leads to heap-based overflow. This vulnerability is uniquely identified as CVE-2026-73863. The attack is possible to be carried out remotely. No exploit exists. The affected component should be upgraded.

Detailsinfo

A vulnerability was found in NanoMQ up to 0.24.13. It has been rated as critical. This issue affects the function nmq_subinfo_decode of the file nng/src/sp/protocol/mqtt/mqtt_parser.c of the component MQTT Parser. The manipulation with an unknown input leads to a heap-based overflow vulnerability. Using CWE to declare the problem leads to CWE-122. A heap overflow condition is a buffer overflow, where the buffer that can be overwritten is allocated in the heap portion of memory, generally meaning that the buffer was allocated using a routine such as malloc(). Impacted is confidentiality, integrity, and availability. The summary by CVE is:

NanoMQ is an MQTT broker. Prior to 0.24.14, NanoMQ's broker-side MQTT v5 nmq_subinfo_decode() function in nng/src/sp/protocol/mqtt/mqtt_parser.c reuses len_of_varint from the outer Properties Length while parsing each SUBSCRIPTION_IDENTIFIER. A remote client can send a SUBSCRIBE packet with a multi-byte Properties Length and repeated subscription identifiers, causing get_var_integer() to begin at an incorrect offset and read beyond the heap message buffer. The flaw is reachable through the broker receive path and can crash the broker, while the separately reported topic-option off-by-one occurs later and is not this vulnerability. This issue is fixed in version 0.24.14.

It is possible to read the advisory at github.com. The identification of this vulnerability is CVE-2026-73863 since 08/13/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Technical details of the vulnerability are known, but there is no available exploit.

Upgrading to version 0.24.14 eliminates this vulnerability.

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Productinfo

Name

• NanoMQ

Version

• 0.24.0
• 0.24.1
• 0.24.2
• 0.24.3
• 0.24.4
• 0.24.5
• 0.24.6
• 0.24.7
• 0.24.8
• 0.24.9
• 0.24.10
• 0.24.11
• 0.24.12
• 0.24.13

Website

• Product: https://github.com/nanomq/nanomq/

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