From b75fcac83c9444884d919b8673591315ec43eb83 Mon Sep 17 00:00:00 2001
From: Michael Niedermayer <michael@niedermayer.cc>
Date: Fri, 24 Oct 2025 20:29:23 +0200
Subject: [PATCH] avformat/rtpenc_h264_hevc: Check space for nal_length_size in
 ff_rtp_send_h264_hevc()

Fixes: memcpy with negative size
Fixes: momo_trip-poc/input

Reported-by: Momoko Shiraishi <shiraishi@os.is.s.u-tokyo.ac.jp>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
(cherry picked from commit d03483bd265b68db00c9b90f6f48dcf61c5c300d)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
---
 libavformat/rtpenc_h264_hevc.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/libavformat/rtpenc_h264_hevc.c b/libavformat/rtpenc_h264_hevc.c
index 0c88fc2a23..470430478b 100644
--- a/libavformat/rtpenc_h264_hevc.c
+++ b/libavformat/rtpenc_h264_hevc.c
@@ -195,6 +195,9 @@ void ff_rtp_send_h264_hevc(AVFormatContext *s1, const uint8_t *buf1, int size)
             r1 = ff_avc_mp4_find_startcode(r, end, s->nal_length_size);
             if (!r1)
                 r1 = end;
+            // Check that the last is not truncated
+            if (r1 - r < s->nal_length_size)
+                break;
             r += s->nal_length_size;
         } else {
             while (!*(r++));