CWE-416: Use After Free
Description
The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.
- Abstraction
- VariantA weakness tied to a specific language, technology or resource.
- Likelihood of exploit
- High
- Status
- Stable
Common consequences
- Integrity
Modify Memory
The use of previously freed memory may corrupt valid data, if the memory area in question has been allocated and used properly elsewhere.
- Availability
DoS: Crash, Exit, or Restart
If chunk consolidation occurs after the use of previously freed data, the process may crash when invalid data is used as chunk information.
- Confidentiality
Read Memory
Read operations on freed memory can sometimes leak sensitive information instead of causing a crash
- IntegrityConfidentialityAvailability
Execute Unauthorized Code or Commands
If malicious data is entered before chunk consolidation can take place, it may be possible to take advantage of a write-what-where primitive to execute arbitrary code. If the newly allocated data happens to hold a class, in C++ for example, various function pointers may be scattered within the heap data. If one of...
Potential mitigations
- Architecture and DesignLanguage Selection
Choose a language that provides automatic memory management.
- ImplementationAttack Surface ReductionEffectiveness: Defense in Depth
When freeing pointers, be sure to set them to NULL once they are freed. However, the utilization of multiple or complex data structures may lower the usefulness of this strategy.
Related weaknesses
CAPEC attack patterns that exploit it
CWE 4.20 links no CAPEC attack pattern to this weakness.