AIS-catcher is a multi-platform AIS receiver. Prior to version 0.64, an integer underflow vulnerability exists in the MQTT parsing logic of AIS-catcher. This vulnerability allows an attacker to trigger a massive Heap Buffer Overflow by sending a malformed MQTT packet with a manipulated Topic Length field. This leads to an immediate Denial of Service (DoS) and, when used as a library, severe Memory Corruption that can be leveraged for Remote Code Execution (RCE). This issue has been patched in version 0.64.