GNU Emacs before 25.3 allows remote attackers to execute arbitrary code via email with crafted "Content-Type: text/enriched" data containing an x-display XML element that specifies execution of shell commands, related to an unsafe text/enriched extension in lisp/textmodes/enriched.el, and unsafe Gnus support for enriched and richtext inline MIME objects in lisp/gnus/mm-view.el. In particular, an Emacs user can be instantly compromised by reading a crafted email message (or Usenet news article).