CVE-2026-53702: Gstreamer1-plugins-bad-free: gstreamer: stack buffer overflow in h.265 buffering period sei parser

A stack buffer overflow flaw was found in the GStreamer H.265 codec parser library (gst-plugins-bad). When parsing a buffering period SEI message, the parser uses an incorrect loop bound derived from cpb_cnt_minus1[i] (the loop index) instead of the sub-layer 0 CPB count cpb_cnt_minus1[0] from the referenced Sequence Parameter Set. A crafted H.265 video file or stream can cause the parser to write beyond the bounds of stack-allocated CPB delay arrays, resulting in a crash or potential stack memory corruption.