CVE-2022-51012 in PocketMine-MP
Summary
by MITRE • 09/07/2026
PocketMine-MP versions before 4.2.9 fail to properly validate NBT data types during deserialization of inventory transaction packets from clients. Attackers can send crafted inventory transactions with malformed NBT tags to trigger server crashes and cause denial of service.
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Analysis
by VulDB Data Team • 09/07/2026
The vulnerability identified in PocketMine-MP versions prior to 4.2.9 represents a critical failure in the input validation mechanisms governing network packet processing, specifically within the deserialization logic for Notch Binary Tag (NBT) data structures associated with inventory transactions. As an open-source Minecraft server software written in PHP, PocketMine-MP relies heavily on parsing binary data streams sent by client applications to synchronize game state. The core technical flaw lies in the insufficient type checking and boundary validation performed when interpreting NBT tags embedded within these transaction packets. When a client sends an inventory update or trade request, the server parses the accompanying NBT payload to determine item counts, metadata, and other attributes. In vulnerable versions, the parser does not strictly enforce expected data types for specific tag identifiers, allowing attackers to inject malformed or unexpectedly typed binary sequences that confuse the internal deserialization routines.
This lack of rigorous validation enables a remote attacker to trigger a denial of service condition by sending specially crafted inventory transaction packets containing invalid NBT structures. Upon receiving such malicious payloads, the server's PHP runtime encounters unexpected data types during type coercion or array access operations, leading to fatal errors that crash the main game loop. Because PocketMine-MP typically runs as a long-lived daemon process handling multiple concurrent connections, a single successful exploit can destabilize the entire server instance, rendering it unavailable to legitimate players. This constitutes a classic example of an improper input validation vulnerability where untrusted data from network sources is processed without adequate sanitization or type enforcement, leading to application instability and service interruption.
From a classification perspective, this flaw aligns with CWE-20 Improper Input Validation, as the system fails to verify that incoming NBT tags conform to expected schemas before processing them. Furthermore, it relates closely to CWE-134 Use of Externally-Controlled Format String if the malformed data leads to parsing errors that expose internal state or crash handlers in a way that could be leveraged for further exploitation, though primarily here it manifests as a stability issue. In terms of offensive security frameworks, this vulnerability is exploitable via MITRE ATT&CK technique T1498 Network Denial of Service, where the attacker utilizes specific network interactions to disrupt service availability rather than compromising confidentiality or integrity directly. The attack vector is remote and requires no authentication if the server port is exposed, making it particularly dangerous for publicly accessible servers that do not implement strict IP whitelisting or advanced firewall rules at the application layer.
The operational impact of this vulnerability extends beyond simple downtime; it affects the reliability and trustworthiness of multiplayer environments hosted on affected versions. Server administrators may experience frequent restarts due to crashes triggered by automated bots or malicious actors scanning for vulnerable instances, leading to increased maintenance overhead and potential loss of player engagement. Additionally, in some PHP configurations, severe errors during deserialization might expose stack traces or internal file paths if error reporting is not strictly disabled, potentially aiding further reconnaissance efforts. The vulnerability underscores the importance of robust serialization libraries that enforce strict schema validation rather than relying on loose typing behaviors inherent to dynamic languages like PHP when processing untrusted binary data from network sockets.
Mitigation strategies primarily involve upgrading PocketMine-MP to version 4.2.9 or later, where developers have implemented stricter NBT type checking and improved error handling during packet deserialization. For administrators unable to upgrade immediately due to plugin compatibility issues, implementing a reverse proxy with deep packet inspection capabilities can help filter out malformed packets before they reach the application server. Additionally, configuring PHP to suppress detailed error messages in production environments reduces information leakage risks associated with crash states. Regularly auditing network traffic for anomalous NBT structures and restricting access to trusted IP ranges further mitigates the risk of exploitation. Ultimately, this incident highlights the necessity of treating all external inputs as hostile and applying defense-in-depth principles that include strict type validation at every stage of data processing within game server architectures.