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PocketMine-MP vulnerable to server crash using badly formatted sign NBT in BlockActorDataPacket

High severity GitHub Reviewed Published Jul 14, 2023 in pmmp/PocketMine-MP • Updated Jul 14, 2023

Package

composer pocketmine/pocketmine-mp (Composer)

Affected versions

>= 4.20.0, < 4.22.3
>= 5.0.0, < 5.2.1

Patched versions

4.22.3
5.2.1

Description

Summary

A player sending a packet can cause the server to crash by providing incorrect sign data in NBT in BlockActorDataPacket.

Details

This vulnerability was discovered using the BlockActorDataPacket, but other packets may also be affected. The player would seem to just need to send an NBT with an incorrect type to throw this error.

[Server thread/CRITICAL]: pocketmine\nbt\UnexpectedTagTypeException: "Expected a tag of type pocketmine\nbt\tag\CompoundTag, got pocketmine\nbt\tag\ByteTag" (EXCEPTION) in "pmsrc/vendor/pocketmine/nbt/src/tag/CompoundTag" at line 107
--- Stack trace ---
  #0 pmsrc/src/network/mcpe/handler/InGamePacketHandler(751): pocketmine\nbt\tag\CompoundTag->getCompoundTag(string[9] FrontText)
  #1 pmsrc/vendor/pocketmine/bedrock-protocol/src/BlockActorDataPacket(50): pocketmine\network\mcpe\handler\InGamePacketHandler->handleBlockActorData(object pocketmine\network\mcpe\protocol\BlockActorDataPacket#220241)
  #2 pmsrc/src/network/mcpe/NetworkSession(433): pocketmine\network\mcpe\protocol\BlockActorDataPacket->handle(object pocketmine\network\mcpe\handler\InGamePacketHandler#190572)

PoC

Use a bot or proxy to send a packet when editing a sign. This packet should contain an NBT with incorrect types but correct architecture.

Impact

This makes it possible to shutdown a server for someone who knows how to operate it. As this was discovered in 4.22.1, everyone with at least this version is affected.

Patches

This bug was fixed by 0c250a2ef09627b48aa52302f6cc7e1f2afb70ea in the 4.22.3 and 5.2.1 releases.

Workarounds

A plugin may be able to handle DataPacketReceiveEvent for BlockActorDataPacket, and verify that the FrontText tag is a TAG_Compound.

References

@dktapps dktapps published to pmmp/PocketMine-MP Jul 14, 2023
Published to the GitHub Advisory Database Jul 14, 2023
Reviewed Jul 14, 2023
Last updated Jul 14, 2023

Severity

High

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
None
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:N/UI:N/S:U/C:N/I:N/A:H

Weaknesses

No CWEs

CVE ID

No known CVE

GHSA ID

GHSA-7wrv-6h42-w54f

Source code

Credits

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