FFmpeg versions 2.1 through 8.1.2 contains a heap buffer overflow vulnerability in the VobSub subtitle demuxer that allows attackers to corrupt adjacent heap memory by supplying a malicious .sub/.idx subtitle file declaring more distinct stream IDs than the fixed-size array bounds in libavformat/mpeg.c. Attackers can craft a subtitle file with excessive distinct stream IDs to trigger unbounded writes beyond the vobsub->q[] array boundary via ff_subtitles_queue_insert(), potentially achieving arbitrary code execution in any application using FFmpeg's VobSub demuxer.
Ubuntu issued USN-8716-2 fixing FFmpeg VobSub, Vulkan HEVC, and NVDEC decoder flaws that could allow denial of service or code execution.
USN-8716-2 provides the Ubuntu 26.04 LTS counterpart to the FFmpeg fixes in USN-8716-1. Crafted media files could cause denial of service or arbitrary code execution through the VobSub subtitle demuxer (CVE-2026-64830), the Vulkan HEVC hardware decoder (CVE-2026-64831), and the NVDEC video decoder path.