PocketMine-MP before 4.2.10 fails to validate the total length of incoming chat message blobs before splitting them by newline characters, allowing attackers to send large messages containing many newlines. Malicious clients can send megabyte-sized chat packets and bombard the server with thousands of such messages, causing server lockups lasting seconds or minutes.

PocketMine-MP before 4.0.7 contains an unhandled exception vulnerability in the ModalFormResponsePacket handler when processing malformed JSON from clients. Attackers can send specially crafted form response packets with invalid JSON to trigger an uncaught InvalidArgumentException, causing server crashes.

PocketMine-MP versions before 5.39.2 contain a network amplification vulnerability in ActorEventPacket handling that allows clients to trigger consuming animations for all visible players. Attackers can send crafted ActorEventPacket messages to spam animation events to other clients and waste server CPU and memory resources.

PocketMine-MP versions before 5.3.1 and 4.23.1 contain a denial of service vulnerability in LoginPacket JSON parsing due to improper null value handling in arrays. Attackers can send malformed JSON with unexpected null elements in LoginPacket to crash the server.

PocketMine-MP versions before 5.39.2 fail to validate entity despawn state when processing attack packets from clients. Attackers can exploit a race condition by attacking a disconnecting player to trigger multiple death handlers, causing inventory items and experience to drop multiple times for duplication.

PocketMine-MP versions before 5.42.1 contain a denial of service vulnerability in the LoginPacket handler that allows remote attackers to flood warning messages by injecting numerous junk properties into the clientData JWT. Attackers can craft malicious login packets with excessive unknown properties to waste server CPU time and degrade performance.

PocketMine-MP before 5.32.1 fails to validate uniqueness of pack UUIDs in ResourcePackClientResponsePacket STATUSSENDPACKS handling, allowing authenticated clients to trigger duplicate pack transmissions. Attackers can send multiple copies of valid pack UUIDs in a single packet to exhaust server memory and cause denial of service.

PocketMine-MP before 5.11.1 contains a denial of service vulnerability in LoginPacket JSON processing that allows remote attackers to crash the server by sending malformed JSON data. Attackers can exploit improper object initialization from scalar JSON types to trigger unset required properties, causing the application to crash.

PocketMine-MP versions before 4.20.5 contain a denial of service vulnerability in LoginPacket JSON parsing due to improper validation in the JsonMapper dependency. Attackers can send malformed JSON structures in LoginPacket to crash the server.

PocketMine-MP versions >= 4.20.0 before 4.22.3 (and before 5.2.1 in the 5.x branch) fail to validate NBT tag types in BlockActorDataPacket. A player can crash the server by sending a packet containing sign NBT data with an incorrect tag type, triggering an unhandled UnexpectedTagTypeException that terminates the server process.

PocketMine-MP before 3.26.5 and 4.0.x before 4.0.5 does not limit book page text length, page count, or author/title length. A player who obtains a writable book can create oversized NBT ('book bombs'), causing excess bandwidth consumption and server crashes (exceeding the 1 MB chunk size limit when saving region-based worlds in PM3, or exceeding the 32 KiB TAGString limit in PM4).