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Book page text, count, and author/title length is not limited in PocketMine-MP

Moderate severity GitHub Reviewed Published Jan 4, 2022 in pmmp/PocketMine-MP • Updated Jan 11, 2023

Package

composer pocketmine/pocketmine-mp (Composer)

Affected versions

< 3.26.5
>= 4.0.0, < 4.0.5

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:

References

@dktapps dktapps published to pmmp/PocketMine-MP Jan 4, 2022
Reviewed Jan 6, 2022
Published to the GitHub Advisory Database Jan 6, 2022
Last updated Jan 11, 2023

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

Weaknesses

No CWEs

CVE ID

No known CVE

GHSA ID

GHSA-p62j-hrxm-xcxf

Source code

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