From: michaelni via ffmpeg-devel <ffmpeg-devel@ffmpeg.org>
To: ffmpeg-devel@ffmpeg.org
Cc: michaelni <code@ffmpeg.org>
Subject: [FFmpeg-devel] [PR] avformat/flvdec: Check *size in cts parsing (PR #21744)
Date: Fri, 13 Feb 2026 01:00:00 -0000
Message-ID: <177094440141.25.1078919601175018061@009cbcb3d8cd> (raw)
PR #21744 opened by michaelni
URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/21744
Patch URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/21744.patch
Fixes: Assertion buf_size >= 0 failed
Fixes: 471553942/clusterfuzz-testcase-minimized-ffmpeg_dem_KUX_fuzzer-5982849812725760
Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
>From 1a9d949b2690f4419c55055f528e378c68526d4f Mon Sep 17 00:00:00 2001
From: Michael Niedermayer <michael@niedermayer.cc>
Date: Thu, 12 Feb 2026 23:10:32 +0100
Subject: [PATCH] avformat/flvdec: Check *size in cts parsing
Fixes: Assertion buf_size >= 0 failed
Fixes: 471553942/clusterfuzz-testcase-minimized-ffmpeg_dem_KUX_fuzzer-5982849812725760
Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
---
libavformat/flvdec.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/libavformat/flvdec.c b/libavformat/flvdec.c
index d10fbf216e..18bdbd18bd 100644
--- a/libavformat/flvdec.c
+++ b/libavformat/flvdec.c
@@ -1775,6 +1775,10 @@ retry_duration:
if (st->codecpar->codec_id == AV_CODEC_ID_MPEG4 ||
((st->codecpar->codec_id == AV_CODEC_ID_H264 || st->codecpar->codec_id == AV_CODEC_ID_HEVC) &&
(!enhanced_flv || type == PacketTypeCodedFrames))) {
+ if (size < 3 || track_size < 3) {
+ ret = AVERROR_INVALIDDATA;
+ goto leave;
+ }
// sign extension
int32_t cts = (avio_rb24(s->pb) + 0xff800000) ^ 0xff800000;
pts = av_sat_add64(dts, cts);
--
2.52.0
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