CWE-761 Detail

The product calls free() on a pointer to a memory resource that was allocated on the heap, but the pointer is not at the start of the buffer.

This can cause the product to crash, or in some cases, modify critical program variables or execute code.

This weakness often occurs when the memory is allocated explicitly on the heap with one of the malloc() family functions and free() is called, but pointer arithmetic has caused the pointer to be in the interior or end of the buffer.

Modes Of Introduction

Implementation

Common Consequences

Observed Examples

Potential Mitigations

Phases : Implementation
When utilizing pointer arithmetic to traverse a buffer, use a separate variable to track progress through memory and preserve the originally allocated address for later freeing.
Phases : Implementation
When programming in C++, consider using smart pointers provided by the boost library to help correctly and consistently manage memory.
Phases : Architecture and Design

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.

Phases : Architecture and Design
Use a language that provides abstractions for memory allocation and deallocation.
Phases : Testing
Use a tool that dynamically detects memory management problems, such as valgrind.

Vulnerability Mapping Notes

Justification : This CWE entry is at the Variant level of abstraction, which is a preferred level of abstraction for mapping to the root causes of vulnerabilities.
Comment : Carefully read both the name and description to ensure that this mapping is an appropriate fit. Do not try to 'force' a mapping to a lower-level Base/Variant simply to comply with this preferred level of abstraction.

NotesNotes

Currently, CWE-763 is the parent, however it may be desirable to have an intermediate parent which is not function-specific, similar to how CWE-762 is an intermediate parent between CWE-763 and CWE-590.

References

REF-657

boost C++ Library Smart Pointers
https://www.boost.org/doc/libs/1_38_0/libs/smart_ptr/smart_ptr.htm

REF-480

Valgrind
http://valgrind.org/

Submission

Modifications