NBTShield

NBTShield is a powerful anti-exploit plugin designed to protect your Paper server from crashes, chunk bans, and privilege escalation attacks.

Paper has tried to address these issues over the years, NBT size caps, book length limits, packet size warnings, compression checks, but every fix was either bypassable or applied too late in the processing pipeline. By the time a Bukkit event fires, the malicious data has already been parsed. NBTShield operates at the Netty level, intercepting raw packets before Paper ever sees them, closing the gap that Paper's own architecture can't easily cover.

Protections included:

🛡️ NBT Protection: blocks oversized or malformed items from entering the server

📖 Book Protection: prevents book-crash exploits (too many pages, oversized data, malicious JSON commands)

🌐 Unicode / PUA Protection: blocks illegal texture pack characters in chat, commands, signs, and items at the Netty packet level — before Bukkit even fires

📦 Packet Protection: low-level interception of PacketTooLarge, VarInt/VarLong overflow, and compression attacks

🗺️ Chunk Protection: scans tile entities and item drops on chunk load to prevent permanent chunk-ban crashes

🤖 Entity Protection: stops item frames and armor stands carrying malicious NBT data from being placed

⚡ OP Exploit Protection: detects and blocks command injection through books, signs, and chat (30+ dangerous patterns)

🔧 Command Block Protection: restricts command block and structure block placement to authorized players

Fully configurable, reload-safe (/nbtreload), and designed for minimal performance impact. Requires Paper 1.21+ · Java 21