Description

The application calls free() on a pointer to memory that was not allocated using associated heap allocation functions such as malloc(), calloc(), or realloc().

When free() is called on an invalid pointer, the program’s memory management data structures may become corrupted. This corruption can cause the program to crash or, in some circumstances, an attacker may be able to cause free() to operate on controllable memory locations to modify critical program variables or execute code.

Modes of Introduction:

– Implementation

Related Weaknesses

CWE-762
CWE-123

Consequences

Integrity, Confidentiality, Availability: Execute Unauthorized Code or Commands, Modify Memory

There is the potential for arbitrary code execution with privileges of the vulnerable program via a “write, what where” primitive. If pointers to memory which hold user information are freed, a malicious user will be able to write 4 bytes anywhere in memory.

Potential Mitigations

Phase: Implementation

Description: 

Only free pointers that you have called malloc on previously. This is the recommended solution. Keep track of which pointers point at the beginning of valid chunks and free them only once.

Phase: Implementation

Description: 

Before freeing a pointer, the programmer should make sure that the pointer was previously allocated on the heap and that the memory belongs to the programmer. Freeing an unallocated pointer will cause undefined behavior in the program.

Phase: Architecture and Design

Description: 

Phase: Architecture and Design

Description: 

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

Phase: Testing

Description: 

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

CVE References