Skip to content

Book page text, count, and author/title length is not limited

Moderate
dktapps published GHSA-p62j-hrxm-xcxf Jan 4, 2022

Package

composer pocketmine/pocketmine-mp (Composer)

Affected versions

*

Patched versions

3.26.5, 4.0.5

Description

Impact

Players can fill book pages with as many characters as they like; the server does not check this.
In addition, the maximum of 50 pages is also not enforced, meaning that players can create "book bombs".

This causes a variety of problems:

  • Oversized NBT on the wire costing excess bandwidth for server and client
  • Server crashes when saving region-based worlds due to exceeding maximum chunk size of 1 MB (PM3-specific)
  • Server crashes if any book page exceeds 32 KiB (due to TAG_String size limit) (PM4-specific)

This does, however, require that an attacker obtain a writable book in the first place in order to exploit the problem.

Patches

The bug has been fixed in 3.26.5 and 4.0.5.

Workarounds

Ban writable books, or use a plugin to cancel PlayerEditBookEvent to cancel the event if strlen(text) > 1024 || mb_strlen(text) > 256.

For more information

If you have any questions or comments about this advisory:

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

CVE ID

No known CVE

Weaknesses

No CWEs