PocketMine-MP before 3.26.5 and 4.0.x before 4.0.5 does not limit book page text length, page count, or author/title length. A player who obtains a writable book can create oversized NBT ('book bombs'), causing excess bandwidth consumption and server crashes (exceeding the 1 MB chunk size limit when saving region-based worlds in PM3, or exceeding the 32 KiB TAG_String limit in PM4).
Attack Parameters
Attack Vector
Network
Can be exploited remotely
Attack Complexity
Low
Easy to exploit
Attack Requirements
None
No additional conditions
Privileges Required
Low
Basic privileges needed
User Interaction
None
No user interaction needed
Impact Assessment
Confidentiality
None
No data leak
Integrity
None
No data modification
Availability
High
Complete denial of service
CVSS Vector v4.0