CVE-2021-21969: Sealevel Seaconnect 370w Firmware

High severity, CVSS 8.1. EPSS: 0.9% chance of exploitation in the next 30 days.

An out-of-bounds write vulnerability exists in the HandleSeaCloudMessage functionality of Sealevel Systems, Inc. SeaConnect 370W v1.3.34. The HandleIncomingSeaCloudMessage function uses at [4] the json_object_get_string to populate the p_payload global variable. The p_payload is only 0x100 bytes long, and the total MQTT message could be up to 0x201 bytes. Because the function json_object_get_string will fill str based on the length of the json’s value and not the actual str size, this would result in a possible out-of-bounds write.

Affected products

• Sealevel Seaconnect 370w Firmware: version 1.3.34 only

Published 2022-02-04. Last modified 2026-06-17.