CVE-2026-73863

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.

• https://github.com/nanomq/NanoNNG/commit/f888fe39d6691b253ff9aee598ce58bbe449ab6f
• https://github.com/nanomq/NanoNNG/pull/1518
• https://github.com/nanomq/nanomq/releases/tag/0.24.14
• https://github.com/nanomq/nanomq/security/advisories/GHSA-pf97-vm7h-q84m
• https://github.com/nanomq/nanomq/security/advisories/GHSA-pf97-vm7h-q84m