A denial of service in the subtitle decoder in FFmpeg 3.2 and 4.1 allows attackers to hog the CPU via a crafted video file in Matroska format, because handleopenbrace in libavcodec/htmlsubtitles.c has a complex format argument to sscanf.
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{
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[
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"threshold": 0.9
},
"id": "CVE-2019-9721-db6040e3",
"target": {
"file": "libavcodec/htmlsubtitles.c"
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"source": "https://git.ffmpeg.org/ffmpeg.git@894995c41e0795c7a44f81adc4838dedc3932e65",
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"digest": {
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"function_hash": "279534106679732723151319424601863156938"
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"id": "CVE-2019-9721-ff8fb535",
"target": {
"function": "handle_open_brace",
"file": "libavcodec/htmlsubtitles.c"
},
"source": "https://git.ffmpeg.org/ffmpeg.git@894995c41e0795c7a44f81adc4838dedc3932e65",
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"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2019-9721.json"
"2026-08-17T05:26:11Z"
{
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"id": "CVE-2019-9721-1e4b4ede",
"target": {
"function": "ff_htmlmarkup_to_ass",
"file": "libavcodec/htmlsubtitles.c"
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"source": "https://github.com/ffmpeg/ffmpeg/commit/273f2755ce8635d42da3cde0eeba15b2e7842774",
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{
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"id": "CVE-2019-9721-efb6ae89",
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"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2019-9721.json"
"2026-08-17T05:26:11Z"