Gstreamer1-plugins-good: gstreamer: integer overflow and out-of-bounds read in qtdemux cea-608 closed-caption parser

A flaw was found in GStreamer's gst-plugins-good isomp4 plugin. When processing a specially crafted MP4 or MOV file containing CEA-608 closed-caption data, an integer overflow in 32-bit unsigned arithmetic can bypass a bounds check in the caption parser. This leads to an out-of-bounds heap read of up to 244 bytes, which is then included in the downstream caption output. An attacker could exploit this by tricking a user into opening a malicious media file, potentially resulting in disclosure of adjacent heap memory or application crash.