MPlayer is a media player capable of playing multiple media formats.
When checking for matching asm rules in the asmrp.c code, the results are stored in a fixed-size array without boundary checks which may allow a buffer overflow.
An attacker can entice a user to connect to a manipulated RTSP server resulting in a Denial of Service and possibly execution of arbitrary code.
There is no known workaround at this time.
All MPlayer users should upgrade to the latest version:
# emerge --sync
# emerge --ask --oneshot --verbose ">=media-video/mplayer-1.0_rc1-r2"