Calling rand() function several times to produce a sequence of pseudorandom numbers will result in generating the same sequence in different runs of the program.

Noncompliant Code Example

 The following code generates a sequence of 10 pseudorandom numbers. No matter how many times this code is executed, it always produces the same sequence.

for (int i=0; i<10; i++)
{
    printf("%d\n", rand()); /* Always generates the same sequence */
}

Compliant Solution

Use srand() before rand() to seed the random sequence generated by rand().

srand(time(NULL)); /* Create seed based on current time */
for (int i=0; i<10; i++)
{
    printf("%d\n", rand()); /* Generates different sequences at different runs */
}

Risk Assessment

 Automated Detection

 TODO

Related Vulnerabilities

 TODO

Other Languages

This recommendation appears in the C++ Secure Coding Standard as MSC19CPP. Use srand() before rand() to generate different sequences of pseudorandom numbers.

References

C++Reference