[MC-77810] Several LAN worlds on the same network can cause a client crash

On a LAN network with several (tested ~100 for fun) worlds open to the same LAN the multiplayer screen has a chance to crash.

This is due to concurrent modification on the collection that stores the results of the UDP lookups (stacktrace below w/ crash report).

For quicker reproduction of the issue, send ~1000 falsified payloads over the network and you will almost certainly get a client crash.

Only known to occur on the multiplayer screen (for obvious reasons).

Attachments

crash-2016-04-28_12.43.14-client.txt

crash-report.txt

Comments 5

StevenNL2000 2015-02-20T12:29:54Z

send ~1000 falsified payloads over the network and you will almost certainly get a client crash

This seems like a way to crash other people's clients. In other words, this might be a security issue.

Travis Ralston 2015-02-21T22:04:15Z

It is a way to crash clients on a localized network in a specific case. It's not a security issue, it's an annoyance at most. The bug does not extend beyond a local network.

kumasasa 2015-11-21T10:59:27Z

Is this still an issue in the current Minecraft Snapshot 15w47c or later? If so, please update the affected versions in order to best aid Mojang ensuring bugs are still valid in the latest releases/pre-releases.

tri blob 2016-04-28T09:48:12Z

Can confirm for 1.9.3-pre2 (I add the crash report above)
I created a program that spam DatagramPacket on the lan broadcast port (4445) with no delay (inside a while true) and when running the program, if the minecraft client in the multiplayer screen, the client will crash

wobst.michael 2016-10-23T17:16:56Z

Is this still an issue in the most recent versions (currently that is 1.10.2, or 16w42a) of Minecraft? If so, please update the affected versions and help us keeping this ticket updated from time to time. If you are the owner/reporter of this ticket, you can modify the affected version(s) yourself.