mgv is a Postscript viewer with a Motif interface, based on Ghostview and GNU gv.
mgv includes code from gv that does not properly boundary check user-supplied data before copying it into process buffers.
An attacker could entice a user to open a specially crafted Postscript document with mgv and possibly execute arbitrary code with the rights of the user running mgv.
There is no known workaround at this time.
mgv is currently unmaintained, and the mgv website no longer exists. As such, the mgv package has been masked in Portage. We recommend that users select an alternate Postscript viewer such as ghostview or GSview, and unmerge mgv:
# emerge --unmerge "app-text/mgv"