Code: int ff_mms_asf_header_parser(MMSContext *mms)
{
    uint8_t *p = mms->asf_header;
    uint8_t *end;
    int flags, stream_id;
    mms->stream_num = 0;

    if (mms->asf_header_size < sizeof(ff_asf_guid) * 2 + 22 ||
        memcmp(p, ff_asf_header, sizeof(ff_asf_guid))) {
        av_log(NULL, AV_LOG_ERROR,
               "Corrupt stream (invalid ASF header, size=%d)\n",
               mms->asf_header_size);
        return AVERROR_INVALIDDATA;
    }

    end = mms->asf_header + mms->asf_header_size;

    p += sizeof(ff_asf_guid) + 14;
    while(end - p >= sizeof(ff_asf_guid) + 8) {
        uint64_t chunksize;
        if (!memcmp(p, ff_asf_data_header, sizeof(ff_asf_guid))) {
            chunksize = 50; // see Reference [2] section 5.1
        } else {
            chunksize = AV_RL64(p + sizeof(ff_asf_guid));
        }
        if (!chunksize || chunksize > end - p) {
            av_log(NULL, AV_LOG_ERROR,
                   "Corrupt stream (header chunksize %"PRId64" is invalid)\n",
                   chunksize);
            return AVERROR_INVALIDDATA;
        }
        if (!memcmp(p, ff_asf_file_header, sizeof(ff_asf_guid))) {
            /* read packet size */
            if (end - p > sizeof(ff_asf_guid) * 2 + 68) {
                mms->asf_packet_len = AV_RL32(p + sizeof(ff_asf_guid) * 2 + 64);
                if (mms->asf_packet_len <= 0 || mms->asf_packet_len > sizeof(mms->in_buffer)) {
                    av_log(NULL, AV_LOG_ERROR,
                           "Corrupt stream (too large pkt_len %d)\n",
                           mms->asf_packet_len);
                    return AVERROR_INVALIDDATA;
                 }
             }
         } else if (!memcmp(p, ff_asf_stream_header, sizeof(ff_asf_guid))) {
            flags     = AV_RL16(p + sizeof(ff_asf_guid)*3 + 24);
            stream_id = flags & 0x7F;
            if (mms->stream_num < MMS_MAX_STREAMS &&
                    46 + mms->stream_num * 6 < sizeof(mms->out_buffer)) {
                mms->streams = av_fast_realloc(mms->streams,
                                   &mms->nb_streams_allocated,
                                   (mms->stream_num + 1) * sizeof(MMSStream));
                if (!mms->streams)
                    return AVERROR(ENOMEM);
                mms->streams[mms->stream_num].id = stream_id;
                mms->stream_num++;
            } else {
                av_log(NULL, AV_LOG_ERROR,
                       "Corrupt stream (too many A/V streams)\n");
                return AVERROR_INVALIDDATA;
             }
         } else if (!memcmp(p, ff_asf_ext_stream_header, sizeof(ff_asf_guid))) {
             if (end - p >= 88) {
                int stream_count = AV_RL16(p + 84), ext_len_count = AV_RL16(p + 86);
                uint64_t skip_bytes = 88;
                while (stream_count--) {
                    if (end - p < skip_bytes + 4) {
                        av_log(NULL, AV_LOG_ERROR,
                               "Corrupt stream (next stream name length is not in the buffer)\n");
                        return AVERROR_INVALIDDATA;
                    }
                    skip_bytes += 4 + AV_RL16(p + skip_bytes + 2);
                }
                while (ext_len_count--) {
                    if (end - p < skip_bytes + 22) {
                        av_log(NULL, AV_LOG_ERROR,
                               "Corrupt stream (next extension system info length is not in the buffer)\n");
                        return AVERROR_INVALIDDATA;
                    }
                    skip_bytes += 22 + AV_RL32(p + skip_bytes + 18);
                }
                if (end - p < skip_bytes) {
                    av_log(NULL, AV_LOG_ERROR,
                           "Corrupt stream (the last extension system info length is invalid)\n");
                    return AVERROR_INVALIDDATA;
                }
                if (chunksize - skip_bytes > 24)
                    chunksize = skip_bytes;
             }
         } else if (!memcmp(p, ff_asf_head1_guid, sizeof(ff_asf_guid))) {
             chunksize = 46; // see references [2] section 3.4. This should be set 46.
         }
         p += chunksize;
     }

    return 0;
}

Vulnerability Type: 
CWE ID: CWE-125
Summary: FFmpeg before commit cced03dd667a5df6df8fd40d8de0bff477ee02e8 contains multiple out of array access vulnerabilities in the mms protocol that can result in attackers accessing out of bound data. This attack appear to be exploitable via network connectivity. This vulnerability appears to have been fixed in cced03dd667a5df6df8fd40d8de0bff477ee02e8 and later.
Commit Message: avformat/mms: Add missing chunksize check

Fixes: out of array read
Fixes: mms-crash-01b6c5d85f9d9f40f4e879896103e9f5b222816a

Found-by: Paul Ch <paulcher@icloud.com>
1st hunk by Paul Ch <paulcher@icloud.com>
Tested-by: Paul Ch <paulcher@icloud.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>