CWE-825 无效指针解引用

Expired Pointer Dereference

结构: Simple

Abstraction: Base

状态: Incomplete

被利用可能性: unkown

基本描述

The program dereferences a pointer that contains a location for memory that was previously valid, but is no longer valid.

扩展描述

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.

相关缺陷

• cwe_Nature: ChildOf cwe_CWE_ID: 119 cwe_View_ID: 1000 cwe_Ordinal: Primary

• cwe_Nature: ChildOf cwe_CWE_ID: 119 cwe_View_ID: 699 cwe_Ordinal: Primary

• cwe_Nature: ChildOf cwe_CWE_ID: 672 cwe_View_ID: 1000

• cwe_Nature: ChildOf cwe_CWE_ID: 672 cwe_View_ID: 699

• cwe_Nature: CanPrecede cwe_CWE_ID: 125 cwe_View_ID: 1000

• cwe_Nature: CanPrecede cwe_CWE_ID: 787 cwe_View_ID: 1000

常见的影响

可能的缓解方案

Architecture and Design

策略:

Choose a language that provides automatic memory management.

Implementation

策略:

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.

示例代码

例

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

bad C

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

例

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

bad C

Double free vulnerabilities have two common (and sometimes overlapping) causes:

None

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.

分析过的案例

Notes

Maintenance
There 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.
Terminology
Many 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.
Research Gap
Under-studied and probably under-reported as of September 2010. This weakness has been reported in high-visibility software, but applied vulnerability researchers have only been investigating it since approximately 2008, and there are only a few public reports. Few reports identify weaknesses at such a low level, which makes it more difficult to find and study real-world code examples.

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