CVE-2020-37277 in PocketMine-MP
Summary
by MITRE • 09/06/2026
PocketMine-MP versions before 3.15.4 contain a denial of service vulnerability in the InventoryTransaction component's findResultItem() method. Malicious clients can send specially crafted InventoryTransactionPackets with multiple conflicting pathways to cause exponential processing complexity, freezing the server.
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Analysis
by VulDB Data Team • 09/06/2026
The identified security flaw resides within PocketMine-MP, a widely used PHP-based Minecraft server implementation, specifically affecting versions prior to 3.15.4. This vulnerability is classified as a denial of service condition triggered by an algorithmic complexity issue within the InventoryTransaction component. The core technical defect lies in the findResultItem() method, which is responsible for processing inventory transactions during gameplay interactions such as item swapping, crafting, or dropping items. When this function receives input packets containing multiple conflicting pathways or ambiguous transaction structures, it fails to efficiently resolve the intended outcome. Instead of terminating early upon detecting an invalid state, the logic proceeds through a recursive or iterative process that expands exponentially with each additional conflict detected in the packet data.
From a technical perspective, this represents a classic case of inefficient algorithmic complexity leading to resource exhaustion. The server's main thread becomes blocked as it attempts to traverse these conflicting logical paths without proper bounds checking or early exit conditions for invalid transaction states. This behavior allows a malicious client to craft specially designed InventoryTransactionPackets that exploit the logic flaw. By sending packets with increasingly complex and contradictory item configurations, an attacker can force the server CPU to consume nearly all available processing power. The result is not merely a slowdown but a complete freeze of the game server, rendering it unresponsive to legitimate players and effectively causing a denial of service for all connected users.
This vulnerability aligns closely with CWE-400, which describes Uncontrolled Resource Consumption, as well as CWE-675, Multiple Operations on a Single Resource without Proper Synchronization or Conflict Detection. In the context of the MITRE ATT&CK framework, this attack vector corresponds to T1499 Endpoint Denial of Service, where an adversary disrupts availability by targeting specific services or applications rather than network infrastructure. The exploitation requires only basic knowledge of Minecraft's packet structure and does not necessitate authentication if the server allows incoming connections from untrusted sources or lacks proper input validation on transaction packets before processing them through the core game logic.
The operational impact of this vulnerability is severe for any PocketMine-MP server operator relying on stable uptime for player retention and economic integrity within their virtual world. A frozen server prevents all gameplay activities, including combat, building, and trading, which can lead to significant loss of trust among the community. Furthermore, because the exploit targets the main thread, it may also prevent administrative commands from being executed, making remote recovery difficult without a hard restart. This lack of resilience highlights critical gaps in input validation and transaction state management within older versions of the software stack.
To mitigate this risk, immediate action is required to upgrade PocketMine-MP to version 3.15.4 or later, where the findResultItem() method has been patched to handle conflicting pathways more efficiently, likely by implementing stricter validation rules that reject ambiguous transactions before they trigger exponential processing loops. Server administrators should also implement rate limiting on packet reception and monitor for unusual spikes in CPU usage associated with inventory-related packets. Additionally, deploying a web application firewall or custom plugin-level input sanitization can provide an extra layer of defense against malformed transaction data until the underlying software is fully updated to address this algorithmic weakness.