libass 0.15.x before 0.15.1 has a heap-based buffer overflow in decode_chars (called from decode_font and process_text) because the wrong integer data type is used for subtraction.
Exploitability
AV:LAC:LPR:NUI:RScope
S:UImpact
C:HI:HA:H7.8/CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H