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In this noncompliant example, the call to fscanf() can result in a write outside the character array buf.:

#include <stdio.h>
 
enum { BUF_LENGTH = 1024 };
 
void get_data(void) {
  char buf[BUF_LENGTH];
  fscanf(stdin, "%s", buf); */
  /* rest of function
}

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In this compliant solution, the call to fscanf() is constrained not to overflow buf.:

#include <stdio.h>
 
enum { BUF_LENGTH = 1024 };
 
void get_data(void) {
  char buf[BUF_LENGTH];
  fscanf(stdin, "%1024s", buf);
  /* rest of function */
}

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Vulnerabilities can occur when inadequate space is allocated to copy a command-line argument or other program input. In this noncompliant code example, an attacker can manipulate the contents of argv[0] can be manipulated by an attacker to cause a buffer overflow:

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The strcpy_s() function provides additional safeguards, including accepting the size of the destination buffer as an additional argument . (See see STR07-C. Use the bounds-checking interfaces for remediation of existing string manipulation code). ) Do not assume that argv[0] is non-null.

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