PocketMine-MP vulnerable to server crash using badly formatted sign NBT in BlockActorDataPacket
The advisory, in context
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.
Affected packages
Start with the recorded fix for your release branch. Check your installed version and test compatibility before upgrading. Fixing this advisory does not rule out other vulnerabilities in the release.
From 4.20.0 before 4.22.3
Fixed in 4.22.3
11 explicitly affected versions
4.20.0, 4.20.1, 4.20.2, 4.20.3, 4.20.4, 4.20.5, 4.21.0, 4.21.1, 4.22.0, 4.22.1, 4.22.2
View affected-version evidence
{
"ranges": [
{
"events": [
{
"introduced": "4.20.0"
},
{
"fixed": "4.22.3"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"4.20.0",
"4.20.1",
"4.20.2",
"4.20.3",
"4.20.4",
"4.20.5",
"4.21.0",
"4.21.1",
"4.22.0",
"4.22.1",
"4.22.2"
]
}From 5.0.0 before 5.2.1
Fixed in 5.2.1
7 explicitly affected versions
5.0.0, 5.0.1, 5.1.0, 5.1.1, 5.1.2, 5.1.3, 5.2.0
View affected-version evidence
{
"ranges": [
{
"events": [
{
"introduced": "5.0.0"
},
{
"fixed": "5.2.1"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"5.0.0",
"5.0.1",
"5.1.0",
"5.1.1",
"5.1.2",
"5.1.3",
"5.2.0"
]
}