CVE-2022-51013 in PocketMine-MP
Summary
by MITRE • 09/07/2026
PocketMine-MP versions before 4.2.3 fail to validate damage metadata values in tool and armor item NBT data received from clients. Attackers can send negative or out-of-range damage values in itemstack NBT to trigger unhandled exceptions in the Durable class, causing server crashes.
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Analysis
by VulDB Data Team • 09/07/2026
The vulnerability identified in PocketMine-MP versions prior to 4.2.3 represents a critical failure in input validation within the game server's handling of networked data structures. Specifically, the flaw resides in how the application processes Notation Binary (NBT) metadata associated with tool and armor items transmitted by connected clients. In multiplayer environments such as Minecraft servers, item stacks are frequently exchanged between players and the server to update inventory states, equip gear, or perform crafting actions. These interactions involve complex data structures that define an item's properties, including its durability level. The PocketMine-MP engine relies on these NBT tags to track how much wear and tear has been applied to virtual items during gameplay. However, in versions before 4.2.3, the server software does not adequately sanitize or validate the integer values contained within the damage metadata field of incoming item stack packets. This lack of rigorous boundary checking allows malicious actors to inject malformed data directly into the game's logic layer without triggering immediate rejection by the network protocol handler.
From a technical perspective, this vulnerability is classified as an Improper Input Validation issue, which aligns with Common Weakness Enumeration identifier CWE-20. When a client sends a damage value that is negative or exceeds the expected maximum durability threshold for a specific item type, the server attempts to process this anomalous data within its internal Durable class. The Durable class is responsible for managing the state of items that degrade over time through use. Because the incoming values fall outside the acceptable range defined by the application's logic, arithmetic operations or conditional checks performed on these values fail unexpectedly. Instead of gracefully handling the error by rejecting the packet or resetting the item to a default state, the unhandled exception propagates up the call stack. This results in an abrupt termination of the server process, effectively causing a Denial of Service condition for all connected players and administrators who rely on the service's availability.
The operational impact of this vulnerability is severe due to its potential for remote exploitation without authentication requirements in many default configurations. An attacker can craft a simple network packet containing a maliciously crafted item stack with extreme negative damage values or excessively large positive integers and send it to the server during any interaction that involves item data, such as dropping an item into the world, trading via villager interfaces, or using specific game mechanics that update item durability. The successful exploitation leads to immediate server crashes, disrupting gameplay for all users on the instance. This type of attack is particularly disruptive because it requires minimal effort from the attacker and can be automated easily, allowing for persistent availability attacks against public servers. In the context of cyber security frameworks like MITRE ATT&CK, this behavior corresponds to techniques related to Resource Hijacking or Denial of Service via application layer exploitation, where the goal is not data theft but rather service disruption through resource exhaustion or process termination.
To mitigate this vulnerability, administrators must upgrade PocketMine-MP to version 4.2.3 or later, as these releases include patches that enforce strict validation on incoming NBT damage values before they are processed by the Durable class. The fix ensures that any value falling outside the predefined bounds for item durability is either clamped to valid limits or rejected entirely with an appropriate error response sent back to the client rather than causing a server-side exception. Additionally, while upgrading software is the primary remediation strategy, network-level defenses such as rate limiting and deep packet inspection can provide supplementary protection by detecting anomalous traffic patterns associated with fuzzing attacks. However, relying solely on perimeter security is insufficient; application-layer validation remains the most effective defense against this class of input validation flaws. Regularly monitoring server logs for unhandled exceptions related to item data processing can also help in identifying potential exploitation attempts before they lead to service outages.