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GHSA-7wrv-6h42-w54f
No affected components available
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.
The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a high impact on the availability of the system.
Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.
Probability that this vulnerability will be exploited in the wild within the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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