static int rtmp_packet_read_one_chunk(URLContext *h, RTMPPacket *p,
                                      int chunk_size, RTMPPacket **prev_pkt_ptr,
                                      int *nb_prev_pkt, uint8_t hdr)
{

    uint8_t buf[16];
    int channel_id, timestamp, size;
    uint32_t ts_field; // non-extended timestamp or delta field
    uint32_t extra = 0;
    enum RTMPPacketType type;
    int written = 0;
    int ret, toread;
    RTMPPacket *prev_pkt;

    written++;
    channel_id = hdr & 0x3F;

    if (channel_id < 2) { //special case for channel number >= 64
        buf[1] = 0;
        if (ffurl_read_complete(h, buf, channel_id + 1) != channel_id + 1)
            return AVERROR(EIO);
        written += channel_id + 1;
        channel_id = AV_RL16(buf) + 64;
    }
    if ((ret = ff_rtmp_check_alloc_array(prev_pkt_ptr, nb_prev_pkt,
                                         channel_id)) < 0)
        return ret;
    prev_pkt = *prev_pkt_ptr;
    size  = prev_pkt[channel_id].size;
    type  = prev_pkt[channel_id].type;
    extra = prev_pkt[channel_id].extra;

    hdr >>= 6; // header size indicator
    if (hdr == RTMP_PS_ONEBYTE) {
        ts_field = prev_pkt[channel_id].ts_field;
    } else {
        if (ffurl_read_complete(h, buf, 3) != 3)
            return AVERROR(EIO);
        written += 3;
        ts_field = AV_RB24(buf);
        if (hdr != RTMP_PS_FOURBYTES) {
            if (ffurl_read_complete(h, buf, 3) != 3)
                return AVERROR(EIO);
            written += 3;
            size = AV_RB24(buf);
            if (ffurl_read_complete(h, buf, 1) != 1)
                return AVERROR(EIO);
            written++;
            type = buf[0];
            if (hdr == RTMP_PS_TWELVEBYTES) {
                if (ffurl_read_complete(h, buf, 4) != 4)
                    return AVERROR(EIO);
                written += 4;
                extra = AV_RL32(buf);
            }
        }
    }
    if (ts_field == 0xFFFFFF) {
        if (ffurl_read_complete(h, buf, 4) != 4)
            return AVERROR(EIO);
        timestamp = AV_RB32(buf);
    } else {
        timestamp = ts_field;
    }
     if (hdr != RTMP_PS_TWELVEBYTES)
         timestamp += prev_pkt[channel_id].timestamp;
 
    if (prev_pkt[channel_id].read && size != prev_pkt[channel_id].size) {
        av_log(NULL, AV_LOG_ERROR, "RTMP packet size mismatch %d != %d\n",
                size,
                prev_pkt[channel_id].size);
        ff_rtmp_packet_destroy(&prev_pkt[channel_id]);
        prev_pkt[channel_id].read = 0;
    }

     if (!prev_pkt[channel_id].read) {
         if ((ret = ff_rtmp_packet_create(p, channel_id, type, timestamp,
                                          size)) < 0)
            return ret;
        p->read = written;
        p->offset = 0;
        prev_pkt[channel_id].ts_field   = ts_field;
        prev_pkt[channel_id].timestamp  = timestamp;
    } else {
        RTMPPacket *prev = &prev_pkt[channel_id];
        p->data          = prev->data;
        p->size          = prev->size;
        p->channel_id    = prev->channel_id;
        p->type          = prev->type;
        p->ts_field      = prev->ts_field;
        p->extra         = prev->extra;
        p->offset        = prev->offset;
        p->read          = prev->read + written;
        p->timestamp     = prev->timestamp;
        prev->data       = NULL;
    }
    p->extra = extra;
    prev_pkt[channel_id].channel_id = channel_id;
    prev_pkt[channel_id].type       = type;
    prev_pkt[channel_id].size       = size;
    prev_pkt[channel_id].extra      = extra;
    size = size - p->offset;

    toread = FFMIN(size, chunk_size);
    if (ffurl_read_complete(h, p->data + p->offset, toread) != toread) {
        ff_rtmp_packet_destroy(p);
        return AVERROR(EIO);
    }
    size      -= toread;
    p->read   += toread;
    p->offset += toread;

    if (size > 0) {
       RTMPPacket *prev = &prev_pkt[channel_id];
       prev->data = p->data;
       prev->read = p->read;
       prev->offset = p->offset;
       p->data      = NULL;
       return AVERROR(EAGAIN);
    }

    prev_pkt[channel_id].read = 0; // read complete; reset if needed
    return p->read;
}

The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.