Expired Pointer Dereference

Incomplete Base
Structure: Simple
Description

The product dereferences a pointer that contains a location for memory that was previously valid, but is no longer valid.

Extended Description

When a product releases memory, but it maintains a pointer to that memory, then the memory might be re-allocated at a later time. If the original pointer is accessed to read or write data, then this could cause the product to read or modify data that is in use by a different function or process. Depending on how the newly-allocated memory is used, this could lead to a denial of service, information exposure, or code execution.

Common Consequences 3
Scope: Confidentiality

Impact: Read Memory

If the expired pointer is used in a read operation, an attacker might be able to control data read in by the application.

Scope: Availability

Impact: DoS: Crash, Exit, or Restart

If the expired pointer references a memory location that is not accessible to the product, or points to a location that is "malformed" (such as NULL) or larger than expected by a read or write operation, then a crash may occur.

Scope: IntegrityConfidentialityAvailability

Impact: Execute Unauthorized Code or Commands

If the expired pointer is used in a function call, or points to unexpected data in a write operation, then code execution may be possible.

Potential Mitigations 2
Phase: Architecture and Design
Choose a language that provides automatic memory management.
Phase: Implementation
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.
Demonstrative Examples 2

ID : DX-71

The following code shows a simple example of a use after free error:

Code Example:

Bad
C
c
When an error occurs, the pointer is immediately freed. However, this pointer is later incorrectly used in the logError function.

ID : DX-72

The following code shows a simple example of a double free error:

Code Example:

Bad
C
c
Double free vulnerabilities have two common (and sometimes overlapping) causes:
- Error conditions and other exceptional circumstances - Confusion over which part of the program is responsible for freeing the memory
Although some double free vulnerabilities are not much more complicated than the previous example, most are spread out across hundreds of lines of code or even different files. Programmers seem particularly susceptible to freeing global variables more than once.
Observed Examples 4
CVE-2008-5013access of expired memory address leads to arbitrary code execution
CVE-2010-3257stale pointer issue leads to denial of service and possibly other consequences
CVE-2008-0062Chain: a message having an unknown message type may cause a reference to uninitialized memory resulting in a null pointer dereference (NULL Pointer Dereference) or dangling pointer (Expired Pointer Dereference), possibly crashing the system or causing heap corruption.
CVE-2007-1211read of value at an offset into a structure after the offset is no longer valid
Applicable Platforms
Languages:
C : UndeterminedC++ : Undetermined
Alternate Terms

Dangling pointer

Functional Areas
  1. Memory Management
Affected Resources
  1. Memory
Notes
MaintenanceThere are close relationships between incorrect pointer dereferences and other weaknesses related to buffer operations. There may not be sufficient community agreement regarding these relationships. Further study is needed to determine when these relationships are chains, composites, perspective/layering, or other types of relationships. As of September 2010, most of the relationships are being captured as chains.
TerminologyMany weaknesses related to pointer dereferences fall under the general term of "memory corruption" or "memory safety." As of September 2010, there is no commonly-used terminology that covers the lower-level variants.