jbig2_pattern_dictionary(Jbig2Ctx *ctx, Jbig2Segment *segment, const byte *segment_data)
{
    Jbig2PatternDictParams params;
    Jbig2ArithCx *GB_stats = NULL;
    byte flags;
    int offset = 0;

    /* 7.4.4.1 - Data header */
    if (segment->data_length < 7) {
        return jbig2_error(ctx, JBIG2_SEVERITY_FATAL, segment->number, "Segment too short");
    }
    flags = segment_data[0];
    params.HDMMR = flags & 1;
    params.HDTEMPLATE = (flags & 6) >> 1;
    params.HDPW = segment_data[1];
    params.HDPH = segment_data[2];
    params.GRAYMAX = jbig2_get_uint32(segment_data + 3);
    offset += 7;

    jbig2_error(ctx, JBIG2_SEVERITY_INFO, segment->number,
                "pattern dictionary, flags=%02x, %d grays (%dx%d cell)", flags, params.GRAYMAX + 1, params.HDPW, params.HDPH);

    if (params.HDMMR && params.HDTEMPLATE) {
        jbig2_error(ctx, JBIG2_SEVERITY_WARNING, segment->number, "HDTEMPLATE is %d when HDMMR is %d, contrary to spec", params.HDTEMPLATE, params.HDMMR);
    }
    if (flags & 0xf8) {
        jbig2_error(ctx, JBIG2_SEVERITY_WARNING, segment->number, "Reserved flag bits non-zero");
    }

    /* 7.4.4.2 */
    if (!params.HDMMR) {
        /* allocate and zero arithmetic coding stats */
        int stats_size = jbig2_generic_stats_size(ctx, params.HDTEMPLATE);

        GB_stats = jbig2_new(ctx, Jbig2ArithCx, stats_size);
        if (GB_stats == NULL) {
            jbig2_error(ctx, JBIG2_SEVERITY_FATAL, segment->number, "failed to allocate GB_stats in pattern dictionary");
            return 0;
        }
        memset(GB_stats, 0, stats_size);
    }

    segment->result = jbig2_decode_pattern_dict(ctx, segment, &params, segment_data + offset, segment->data_length - offset, GB_stats);

    /* todo: retain GB_stats? */
    if (!params.HDMMR) {
        jbig2_free(ctx->allocator, GB_stats);
    }

    return (segment->result != NULL) ? 0 : -1;
}

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.