An example of a global buffer overflow with reading sensitive data, see more on https://blog.gypsyengineer.com/fun/security/global-buffer-overflows.html

gbo.c

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
 
char secret[32];
char public[32];
 
void print_strings(char *buffer, int len) {
    for (int i=0; i<len; i++) {
        if (buffer[i] != 0) {
            printf("%c", buffer[i]);
        }
    }
    printf("\n");
}
 
int main(int argc, char **argv) {
    if(argc < 2) {
        printf("no parameters specified\n");
        exit(-1);
    }
 
    strcpy(secret, "This is a secret");
    strcpy(public, "This is public data");
 
    // convert first parameter to an integer
    int len = atoi(argv[1]);
 
    // allocate a local buffer
    // reserve one byte for \0 symbol
    char buffer[len+1];
 
    // global buffer overread may occur here
    // if `len` is more than length of `public`
    memcpy(buffer, public, len);
    buffer[len] = 0;
 
    print_strings(buffer, len);
}