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The formatted output functions (fprintf() and related functions) convert, format, and print their arguments under control of a format string, defined as follows by the C Standard, subclause 7.21.6.1, paragraph 3 [ISO/IEC 9899:2011]:

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#include <stdio.h>
 
void func(void) {
  const char *error_msg = "Resource not available to user.";
  int error_type = 3;
  /* ... */
  printf("Error (type %s): %d\n", error_type, error_msg);
  /* ... */
}

Compliant Solution

This compliant solution ensures that the format arguments match their respective format specifications:

#include <stdio.h>
 
void func(void) {
  const char *error_msg = "Resource not available to user.";
  int error_type = 3;
  /* ... */
  printf("Error (type %d): %s\n", error_type, error_msg);

  /* ... */
}

Risk Assessment

In most cases, incorrectly specified format strings will result in abnormal program termination. However, in some cases they can be used to corrupt memory in manners controllable by an attacker.

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