CWE-789: Uncontrolled Memory Allocation
The product allocates memory based on an untrusted size value, but it does not validate or incorrectly validates the size, allowing arbitrary amounts of memory to be allocated.
The table(s) below shows the weaknesses and high level categories that are related to this weakness. These relationships are defined as ChildOf, ParentOf, MemberOf and give insight to similar items that may exist at higher and lower levels of abstraction. In addition, relationships such as PeerOf and CanAlsoBe are defined to show similar weaknesses that the user may want to explore.
Relevant to the view "Research Concepts" (CWE-1000)
The different Modes of Introduction provide information about how and when this weakness may be introduced. The Phase identifies a point in the life cycle at which introduction may occur, while the Note provides a typical scenario related to introduction during the given phase.
The listings below show possible areas for which the given weakness could appear. These may be for specific named Languages, Operating Systems, Architectures, Paradigms, Technologies, or a class of such platforms. The platform is listed along with how frequently the given weakness appears for that instance.
C (Undetermined Prevalence)
C++ (Undetermined Prevalence)
Class: Language-Independent (Undetermined Prevalence)
The table below specifies different individual consequences associated with the weakness. The Scope identifies the application security area that is violated, while the Impact describes the negative technical impact that arises if an adversary succeeds in exploiting this weakness. The Likelihood provides information about how likely the specific consequence is expected to be seen relative to the other consequences in the list. For example, there may be high likelihood that a weakness will be exploited to achieve a certain impact, but a low likelihood that it will be exploited to achieve a different impact.
Consider the following code, which accepts an untrusted size value and allocates a buffer to contain a string of the given size.
Example Language: C
unsigned int size = GetUntrustedInt();
/* ignore integer overflow (CWE-190) for this example */
unsigned int totBytes = size * sizeof(char);
char *string = (char *)malloc(totBytes);
Suppose an attacker provides a size value of:
This will cause 305,419,896 bytes (over 291 megabytes) to be allocated for the string.
Consider the following code, which accepts an untrusted size value and uses the size as an initial capacity for a HashMap.
Example Language: Java
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.
The following code obtains an untrusted number that it used as an index into an array of messages.
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.
This MemberOf Relationships table shows additional CWE Categories and Views that reference this weakness as a member. This information is often useful in understanding where a weakness fits within the context of external information sources.
Uncontrolled memory allocation is possible in many languages, such as dynamic array allocation in perl or initial size parameters in Collections in Java. However, languages like C and C++ where programmers have the power to more directly control memory management will be more susceptible.
This weakness can be closely associated with integer overflows (CWE-190). Integer overflow attacks would concentrate on providing an extremely large number that triggers an overflow that causes less memory to be allocated than expected. By providing a large value that does not trigger an integer overflow, the attacker could still cause excessive amounts of memory to be allocated.
More information is available — Please select a different filter.