Release of Invalid Pointer or Reference

Incomplete Base

Structure: Simple

Description

This vulnerability occurs when a program tries to free a memory resource back to the system but uses an incorrect deallocation method or calls the correct method improperly.

Extended Description

This issue typically arises from mismatched memory management functions. For example, memory allocated with one function (like `malloc`) is incorrectly freed using a non-compatible function from a different API (like `delete`), leading to heap corruption and instability. This mismatch, often called CWE-762, breaks the underlying memory manager's expectations. Even when using the correct function pair, developers can misuse them. A common mistake is calling the deallocation function with an invalid pointer—such as one that was already freed, points to stack memory, or was never allocated. This scenario, related to CWE-761, causes crashes or undefined behavior because the system cannot process the flawed release request.

Common Consequences 1

Scope: IntegrityAvailabilityConfidentiality

Impact: Modify MemoryDoS: Crash, Exit, or RestartExecute Unauthorized Code or Commands

This weakness may result in the corruption of memory, and perhaps instructions, possibly leading to a crash. If the corrupted memory can be effectively controlled, it may be possible to execute arbitrary code.

Detection Methods 1

FuzzingHigh

Fuzz testing (fuzzing) is a powerful technique for generating large numbers of diverse inputs - either randomly or algorithmically - and dynamically invoking the code with those inputs. Even with random inputs, it is often capable of generating unexpected results such as crashes, memory corruption, or resource consumption. Fuzzing effectively produces repeatable test cases that clearly indicate bugs, which helps developers to diagnose the issues.

Potential Mitigations 5

Phase: Implementation

Only call matching memory management functions. Do not mix and match routines. For example, when you allocate a buffer with malloc(), dispose of the original pointer with free().

Phase: Implementation

When programming in C++, consider using smart pointers provided by the boost library to help correctly and consistently manage memory.

Phase: Architecture and Design

Strategy: Libraries or Frameworks

Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. For example, glibc in Linux provides protection against free of invalid pointers.

Phase: Architecture and Design

Use a language that provides abstractions for memory allocation and deallocation.

Phase: Testing

Use a tool that dynamically detects memory management problems, such as valgrind.

Demonstrative Examples 4

ID : DX-78

This code attempts to tokenize a string and place it into an array using the strsep function, which inserts a \0 byte in place of whitespace or a tab character. After finishing the loop, each string in the AP array points to a location within the input string.

Code Example:Bad
C
c

Since strsep is not allocating any new memory, freeing an element in the middle of the array is equivalent to free a pointer in the middle of inputstring.

ID : DX-80

This example allocates a BarObj object using the new operator in C++, however, the programmer then deallocates the object using free(), which may lead to unexpected behavior.

Code Example:

Bad

C++

c++

/* do some work with ptr here /

c++

Instead, the programmer should have either created the object with one of the malloc family functions, or else deleted the object with the delete operator.

Code Example:

Good

C++

c++

/* do some work with ptr here /

c++

ID : DX-77

In this example, the programmer dynamically allocates a buffer to hold a string and then searches for a specific character. After completing the search, the programmer attempts to release the allocated memory and return SUCCESS or FAILURE to the caller. Note: for simplification, this example uses a hard-coded "Search Me!" string and a constant string length of 20.

Code Example:

Bad

/* matched char, free string and return success / free(str); return SUCCESS;}

However, if the character is not at the beginning of the string, or if it is not in the string at all, then the pointer will not be at the start of the buffer when the programmer frees it.

Instead of freeing the pointer in the middle of the buffer, the programmer can use an indexing pointer to step through the memory or abstract the memory calculations by using array indexing.

Code Example:

Good

/* matched char, free string and return success / free(str); return SUCCESS;}

ID : DX-79

Consider the following code in the context of a parsing application to extract commands out of user data. The intent is to parse each command and add it to a queue of commands to be executed, discarding each malformed entry.

Code Example:

Bad

//hardcode input length for simplicity* char* input = (char*) malloc(40*sizeof(char)); char tok; char sep = " \t";

While the above code attempts to free memory associated with bad commands, since the memory was all allocated in one chunk, it must all be freed together.

One way to fix this problem would be to copy the commands into a new memory location before placing them in the queue. Then, after all commands have been processed, the memory can safely be freed.

Code Example:

Good

//hardcode input length for simplicity* char* input = (char*) malloc(40*sizeof(char)); char *tok, command; char sep = " \t";

Observed Examples 1

CVE-2019-11930function "internally calls 'calloc' and returns a pointer at an index... inside the allocated buffer. This led to freeing invalid memory."

References 2

boost C++ Library Smart Pointers

https://www.boost.org/doc/libs/1_38_0/libs/smart_ptr/smart_ptr.htm(2023-04-07)

ID: REF-657

Valgrind

https://valgrind.org/(2025-07-24)

ID: REF-480

Applicable Platforms

Languages:

C : OftenC++ : Often

Modes of Introduction

Implementation

Functional Areas

Memory Management

Affected Resources

Memory

Related Weaknesses

ChildOf:

Improper Resource Shutdown or Release (CWE-404)

ChildOf:

Improper Resource Shutdown or Release (CWE-404)

ChildOf:

Improper Resource Shutdown or Release (CWE-404)

Taxonomy Mapping

Software Fault Patterns

Notes

MaintenanceThe view-1000 subtree that is associated with this weakness needs additional work. Several entries will likely be created in this branch. Currently the focus is on free() of memory, but delete and other related release routines may require the creation of intermediate entries that are not specific to a particular function. In addition, the role of other types of invalid pointers, such as an expired pointer, i.e. Double Free Double Free and release of uninitialized pointers, related to Use of Uninitialized Variable.