CVE-2026-73473: Gstreamer1-plugins-good: gstreamer: missing subindex entry count validation in avidemux leading to denial of service

A flaw was found in GStreamer gst-plugins-good (avidemux). In the subindex parser, missing validation of the entry count can cause excessive memory allocation and denial of service. Because avidemux is auto-plugged by playbin, decodebin, and gst-discoverer, opening or previewing a crafted AVI is sufficient to trigger the issue. Fixed upstream in gst-plugins-good 1.28.6 (GStreamer-SA-2026-0072).