static size_t htmlencode (const char *src, char **dest) {
    const char *amp = "&amp;";
    const char *lt  = "&lt;";
    const char *gt  = "&gt;";
    const char *start;
    char *tmp;
    size_t final_size = 0;

    if (!src)
        return 0;

    start = src;

    /* Compute needed dest size */
    while (*src != '\0') {
        switch(*src) {
            case 38: /* & */
                final_size += 5;
                break;
            case 60: /* < */
            case 62: /* > */
                final_size += 4;
                break;
            default:
                final_size++;
        }
        src++;
    }

    src = start;
    *dest = av_mallocz(final_size + 1);
    if (!*dest)
        return 0;

    /* Build dest */
    tmp = *dest;
    while (*src != '\0') {
        switch(*src) {
            case 38: /* & */
                cp_html_entity (tmp, amp);
                tmp += 5;
                break;
            case 60: /* < */
                cp_html_entity (tmp, lt);
                tmp += 4;
                break;
            case 62: /* > */
                cp_html_entity (tmp, gt);
                tmp += 4;
                break;
            default:
                *tmp = *src;
                tmp += 1;
        }
        src++;
    }
    *tmp = '\0';

    return final_size;
}

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.