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CWE
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Expired Pointer Dereference

ID: 825Date: (C)2012-05-14   (M)2012-11-08
Type: weaknessStatus: INCOMPLETE
Abstraction Type: Base





Description

The program dereferences a pointer that contains a location for memory that was previously valid, but is no longer valid.

Extended Description

When a program 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 program 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.

Applicable Platforms
None

Common Consequences

ScopeTechnical ImpactNotes
Confidentiality
 
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.
 
Availability
 
DoS: crash / exit / restart
 
If the expired pointer references a memory location that is not accessible to the program, 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.
 
Integrity
Confidentiality
Availability
 
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.
 

Detection Methods
None

Potential Mitigations

PhaseStrategyDescriptionEffectivenessNotes
Architecture and Design
 
 Choose a language that provides automatic memory management.
 
  
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.
 
  

Relationships

Related CWETypeViewChain
CWE-825 CanPrecede CWE-787 Weakness CWE-1000  

Demonstrative Examples   (Details)

  1. The following code shows a simple example of a double free error: (Demonstrative Example Id DX-72)
  2. The following code shows a simple example of a use after free error: (Demonstrative Example Id DX-71)

Observed Examples

  1. CVE-2008-5013 : access of expired memory address leads to arbitrary code execution
  2. CVE-2010-3257 : stale pointer issue leads to denial of service and possibly other consequences
  3. CVE-2007-1211 : read of value at an offset into a structure after the offset is no longer valid

For more examples, refer to CVE relations in the bottom box.

White Box Definitions
None

Black Box Definitions
None

Taxynomy Mappings
None

References:
None

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