This issue was originally reported on the Craftbukkit Leaky:
https://bukkit.atlassian.net/browse/BUKKIT-2459
The original reporter was MonsieurApple.

When more than 128 players are online, the array of players will not be sent in response to an RCON query because of a buffer overflow.
This could be fixed by using an int instead of a byte (which has an upward limit of 128) when looping through the list of players.

https://github.com/ProjectAres/SportBukkit/blob/master/CraftBukkit/QueryBufferOverflowFix.patch

The issue was closed as outside the scope of CraftBukkit, as the file in that patch does not decompile properly and therefore is unsuitable for inclusion in the project.