Minecraft error code when trying to join a specific server?

All of the sudden, I can't log in to a minecraft server. When I log in, I spawn for half a second and get kicked immediately with the following error code
Internal Exception: io.netty.handler.codec.decoderexception:… + length(1) exceeds writerIndex(9): UnpooledHeapByteBuf(ridx: 9, widx: 9, cap: 9)
any solution?

Sounds like the server is using a Mod you don't have.