CVE-2023-54396 in PocketMine-MP
Summary
by MITRE • 09/09/2026
PocketMine-MP versions before 4.8.1 fail to validate dye color IDs in banner NBT data during deserialization. Attackers can provide invalid color values in inventory transactions or via commands to trigger undefined offset errors and crash the server.
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Analysis
by VulDB Data Team • 09/09/2026
The vulnerability identified in PocketMine-MP prior to version 4.8.1 represents a critical input validation failure within the network protocol handling subsystem, specifically targeting the deserialization of Notchian Binary Tag (NBT) data associated with banner items. As a widely used Minecraft server software written in PHP, PocketMine-MP relies on parsing complex binary structures sent by clients to reconstruct game state objects such as player inventories and item stacks. During this process, the application attempts to map integer color identifiers found within the NBT payload of a banner item to specific dye colors defined internally by the engine. The core technical flaw lies in the absence of rigorous bounds checking or type validation before these values are used as array indices or enumeration keys. When an attacker constructs a malicious packet containing a banner with an invalid, negative, or excessively large color ID, the server attempts to access this value within its internal dye mapping structure without verifying if the index exists.
This lack of input sanitization directly leads to undefined offset errors during runtime execution. In PHP environments, accessing an array key that does not exist typically triggers a warning and can result in unexpected behavior or script termination depending on error handling configurations. However, in the context of a persistent server process like PocketMine-MP, this specific failure mode manifests as a crash or severe instability rather than a graceful error message. The operational impact is significant because it allows for a straightforward Denial of Service attack against any server running vulnerable versions. An attacker does not require authentication to exploit this flaw if they can interact with the inventory system through legitimate gameplay mechanics that allow item manipulation, such as trading, dropping items into world chunks, or using specific command-line interfaces that accept NBT data directly. By simply sending a crafted packet during an inventory transaction or via a console command, the malicious actor forces the server to process malformed data, leading to immediate service disruption and requiring manual intervention to restart the application.
From a classification perspective, this vulnerability aligns with CWE-20 Improper Input Validation, as the system fails to verify that user-supplied input conforms to expected constraints before processing it. Furthermore, because the exploit involves sending crafted network packets to trigger a crash in a remote service without requiring prior authentication or complex social engineering, it is categorized under MITRE ATT&CK technique T1498 Network Denial of Service, specifically within the sub-technique for direct network-based attacks. The simplicity of the attack vector makes this vulnerability particularly dangerous in public-facing environments where automated scanners or malicious actors can easily probe for weaknesses by sending malformed NBT structures over the standard Minecraft protocol port.
Mitigation strategies must focus on immediate patching and defensive coding practices. Server administrators should upgrade PocketMine-MP to version 4.8.1 or later, as this release includes patches that enforce strict type checking and bounds validation on all incoming NBT data related to item metadata. For environments where upgrading is not immediately feasible, network-level filtering can provide a temporary layer of defense by inspecting inbound packets for anomalous integer values in banner color fields before they reach the application logic. Additionally, developers should implement robust error handling mechanisms that catch deserialization exceptions and log them securely without exposing stack traces to clients, thereby preventing information leakage while maintaining service availability during partial failures. Regular security audits focusing on binary protocol parsing are essential to prevent similar input validation flaws from being introduced in future updates or custom plugins.