When receiving a text message from a client, the Relay plugin builds a partial buffer until the end of text is found.
There is no limit for the allocated buffer.
A malicious client sending large amount of data without end of text can lead to memory exhaustion and the WeeChat process can be killed by the OOM killer.
Mitigation
Unload relay plugin with command: /plugin unload relay and see: /help weechat.plugin.autoload.