COMMON WEAKNESS ENUMERATIONIncomplete

CWE-825

Expired Pointer Dereference

The product dereferences a pointer that contains a location for memory that was previously valid, but is no longer valid.

Abstraction

Base

Structure

Simple

Likelihood of Exploit

Medium

Understand the problem

What is the problem?

The product dereferences a pointer that contains a location for memory that was previously valid, but is no longer valid.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

Terminology

Alternate terms and usages

Dangling pointer

Root cause

How and when does the problem arise?

Lifecycle phase

Implementation

Risk

What does successful exploitation lead to?

Read Memory

Affected security scopes: Confidentiality

If the expired pointer is used in a read operation, an attacker might be able to control data read in by the application.
DoS: Crash, Exit, or Restart

Affected security scopes: Availability

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.
Execute Unauthorized Code or Commands

Affected security scopes: Integrity, Confidentiality, Availability

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.

Defence

How is it prevented and fixed?

Architecture and Design

Architecture and design approach

Detail
Choose a language that provides automatic memory management.

Implementation

Implementation-phase defence

Detail
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.

Verification

How is it detected?

Automated Static Analysis

Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc.)

Automated Dynamic Analysis

Moderate
Use tools that are integrated during compilation to insert runtime error-checking mechanisms related to memory safety errors, such as AddressSanitizer (ASan) for C/C++ [REF-1518].

Crafted inputs are necessary to reach the code containing the error, such as generated by fuzzers. Also, these tools may reduce performance, and they only report the error condition - not the original mistake that led to the error.