Ruby before 2.4.3 allows Net::FTP command injection. Net::FTP#get, getbinaryfile, gettextfile, put, putbinaryfile, and puttextfile use Kernel#open to open a local file. If the localfile argument starts with the "|" pipe character, the command following the pipe character is executed. The default value of localfile is File.basename(remotefile), so malicious FTP servers could cause arbitrary comman ...
The parser_yyerror function in the UTF-8 parser in Ruby 2.4.1 allows attackers to cause a denial of service (invalid write or read) or possibly have unspecified other impact via a crafted Ruby script, related to the parser_tokadd_utf8 function in parse.y. NOTE: this might have security relevance as a bypass of a $SAFE protection mechanism.