setup_signal(int signr, sigfunc *shandler) {
    struct sigaction nh, oh;

    nh.sa_handler = shandler;
    sigemptyset(&nh.sa_mask);
    nh.sa_flags = 0;

    if(sigaction(signr, &nh, &oh) < 0)
        return SIG_ERR;

    return NULL;
}

This category addresses vulnerabilities caused by flawed access control mechanisms, where incorrect permission settings allow unauthorized users to access restricted resources.