A flaw was found in the SRT and WebVTT subtitle parser in GStreamer's gst-plugins-base. While sanitizing inline subtitle markup, the parser repeatedly searches the remaining text with unanchored regular expressions. A crafted subtitle cue with a long line of unmatched markup-like text can force quadratic CPU use and make a GStreamer-based application unresponsive.
Update gst-plugins-base to version 1.28.2 or later. Where updating is not yet possible, applications that do not require untrusted SRT/WebVTT subtitles can prevent automatic selection of the subparse element (for example, by setting GST_PLUGIN_FEATURE_RANK=subparse:NONE).