Improperly Controlled Sequential Memory Allocation

The product manages a group of objects or resources and performs a separate memory allocation for each object, but it does not properly limit the total amount of memory that is consumed by all of the combined objects.


Description

While the product might limit the amount of memory that is allocated in a single operation for a single object (such as a malloc of an array), if an attacker can cause multiple objects to be allocated in separate operations, then this might cause higher total memory consumption than the developer intended, leading to a denial of service.

Demonstrations

The following examples help to illustrate the nature of this weakness and describe methods or techniques which can be used to mitigate the risk.

Note that the examples here are by no means exhaustive and any given weakness may have many subtle varieties, each of which may require different detection methods or runtime controls.

Example One

This example contains a small allocation of stack memory. When the program was first constructed, the number of times this memory was allocated was probably inconsequential and presented no problem. Over time, as the number of objects in the database grow, the number of allocations will grow - eventually consuming the available stack, i.e. "stack exhaustion." An attacker who is able to add elements to the database could cause stack exhaustion more rapidly than assumed by the developer.

// Gets the size from the number of objects in a database, which over time can conceivably get very large
int end_limit = get_nmbr_obj_from_db();
int i;
int *base = NULL;
int *p =base;
for (i = 0; i < end_limit; i++)
{

  *p = alloca(sizeof(int *));  // Allocate memory on the stack
  p = *p;  // // Point to the next location to be saved

}

Since this uses alloca(), it allocates memory directly on the stack. If end_limit is large enough, then the stack can be entirely consumed.

See Also

Comprehensive CWE Dictionary

This view (slice) covers all the elements in CWE.

Weaknesses without Software Fault Patterns

CWE identifiers in this view are weaknesses that do not have associated Software Fault Patterns (SFPs), as covered by the CWE-888 view. As such, they represent gaps in...

Weaknesses Introduced During Implementation

This view (slice) lists weaknesses that can be introduced during implementation.


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