Example 1
Consider the following code, which accepts an untrusted size value
and allocates a buffer to contain a string of the given size.
unsigned int size = GetUntrustedInt();
/* ignore integer overflow (CWE-190) for this example
*/
unsigned int totBytes = size * sizeof(char);
char *string = (char *)malloc(totBytes);
InitializeString(string);
Suppose an attacker provides a size value of:
This will cause 305,419,896 bytes (over 291 megabytes) to be allocated
for the string.
Example 2
Consider the following code, which accepts an untrusted size value
and uses the size as an initial capacity for a HashMap.
unsigned int size = GetUntrustedInt();
HashMap list = new HashMap(size);
The HashMap constructor will verify that the initial capacity is not
negative, however there is no check in place to verify that sufficient
memory is present. If the attacker provides a large enough value, the
application will run into an OutOfMemoryError.
Example 3
The following code obtains an untrusted number that it used as an
index into an array of messages.
(Bad Code)
Example
Language: Perl
my $num = GetUntrustedNumber();
my @messages = ();
$messages[$num] = "Hello World";
The index is not validated at all (CWE-129), so it might be possible for an attacker to modify an element in @messages that was not intended. If an index is used that is larger than the current size of the array, the Perl interpreter automatically expands the array so that the large index works.
If $num is a large value such as 2147483648 (1<<31),
then the assignment to $messages[$num] would attempt to create a very
large array, then eventually produce an error message such as:
Out of memory during array extend
This memory exhaustion will cause the Perl program to exit, possibly a
denial of service. In addition, the lack of memory could also prevent
many other programs from successfully running on the system.
Description
