When processing subtitles format media file, KMPlayer version 2018.12.24.14 or lower doesn't check object size correctly, which leads to integer underflow then to memory out-of-bound read/write. An attacker can exploit this issue by enticing an unsuspecting user to open a malicious file.
https://www.boho.or.kr/krcert/secNoticeView.do?bulletin_writing_sequence=34991