Overview

If too few arguments are sent to a function, the function will still pop the expected number of arguments from the stack. Potentially, a variable number of arguments could be exhausted in a function as well.

Consequences

• Authorization: There is the potential for arbitrary code execution with privileges of the vulnerable program if function parameter list is exhausted.

• Availability: Potentially a program could fail if it needs more arguments then are available.

Exposure period

• Implementation: This is a simple logical flaw created at implementation time.

Platform

• Languages: C or C++

• Operating platforms: Any

Required resources

Any

Severity

High

Likelihood of exploit

High

Avoidance and mitigation

• Implementation: Forward declare all functions. This is the recommended solution. Properly forward declaration of all used functions will result in a compiler error if too few arguments are sent to a function.

Discussion

This issue can be simply combated with the use of proper build process.

Examples

In C or C++:

foo_funct(one, two);

void foo_funct(int one, int two, int three) {
  printf("1) %d\n2) %d\n3) %d\n", one, two, three);
}

This can be exploited to disclose information with no work whatsoever. In fact, each time this function is run, it will print out the next 4 bytes on the stack after the two numbers sent to it.

Another example in C/C++ is:

void some_function(int foo, ...) {
    int a[3], i;
    va_list ap;

    va_start(ap, foo);
	for (i = 0;  i < sizeof(a) / sizeof(int);  i++)
        a[i] = va_arg(ap, int);
    va_end(ap);
}

int main(int argc, char *argv[]) {
    some_function(17, 42);
}