CWE

Common Weakness Enumeration

A Community-Developed List of Software Weakness Types

CWE/SANS Top 25 Most Dangerous Software Errors
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ID

CWE-188: Reliance on Data/Memory Layout

Weakness ID: 188
Abstraction: Base
Structure: Simple
Status: Draft
Presentation Filter:
+ Description
The software makes invalid assumptions about how protocol data or memory is organized at a lower level, resulting in unintended program behavior.
+ Extended Description

When changing platforms or protocol versions, data may move in unintended ways. For example, some architectures may place local variables A and B right next to each other with A on top; some may place them next to each other with B on top; and others may add some padding to each. The padding size may vary to ensure that each variable is aligned to a proper word size.

In protocol implementations, it is common to calculate an offset relative to another field to pick out a specific piece of data. Exceptional conditions, often involving new protocol versions, may add corner cases that change the data layout in an unusual way. The result can be that an implementation accesses an unintended field in the packet, treating data of one type as data of another type.

+ Relationships

The table(s) below shows the weaknesses and high level categories that are related to this weakness. These relationships are defined as ChildOf, ParentOf, MemberOf and give insight to similar items that may exist at higher and lower levels of abstraction. In addition, relationships such as PeerOf and CanAlsoBe are defined to show similar weaknesses that the user may want to explore.

+ Relevant to the view "Research Concepts" (CWE-1000)
+ Relevant to the view "Development Concepts" (CWE-699)
NatureTypeIDName
MemberOfCategoryCategory137Representation Errors
+ Modes Of Introduction

The different Modes of Introduction provide information about how and when this weakness may be introduced. The Phase identifies a point in the software life cycle at which introduction may occur, while the Note provides a typical scenario related to introduction during the given phase.

PhaseNote
Architecture and Design
Implementation
+ Applicable Platforms
The listings below show possible areas for which the given weakness could appear. These may be for specific named Languages, Operating Systems, Architectures, Paradigms, Technologies, or a class of such platforms. The platform is listed along with how frequently the given weakness appears for that instance.

Languages

C (Undetermined Prevalence)

C++ (Undetermined Prevalence)

+ Common Consequences

The table below specifies different individual consequences associated with the weakness. The Scope identifies the application security area that is violated, while the Impact describes the negative technical impact that arises if an adversary succeeds in exploiting this weakness. The Likelihood provides information about how likely the specific consequence is expected to be seen relative to the other consequences in the list. For example, there may be high likelihood that a weakness will be exploited to achieve a certain impact, but a low likelihood that it will be exploited to achieve a different impact.

ScopeImpactLikelihood
Integrity
Confidentiality

Technical Impact: Modify Memory; Read Memory

Can result in unintended modifications or exposure of sensitive memory.
+ Likelihood Of Exploit
Low
+ Demonstrative Examples

Example 1

In this example function, the memory address of variable b is derived by adding 1 to the address of variable a. This derived address is then used to assign the value 0 to b.

(bad code)
Example Language:
void example() {
char a;
char b;
*(&a + 1) = 0;

}

Here, b may not be one byte past a. It may be one byte in front of a. Or, they may have three bytes between them because they are aligned on 32-bit boundaries.

+ Potential Mitigations

Phases: Implementation; Architecture and Design

In flat address space situations, never allow computing memory addresses as offsets from another memory address.

Phase: Architecture and Design

Fully specify protocol layout unambiguously, providing a structured grammar (e.g., a compilable yacc grammar).

Phase: Testing

Testing: Test that the implementation properly handles each case in the protocol grammar.
+ Memberships
This MemberOf Relationships table shows additional CWE Categories and Views that reference this weakness as a member. This information is often useful in understanding where a weakness fits within the context of external information sources.
NatureTypeIDName
MemberOfCategoryCategory977SFP Secondary Cluster: Design
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
CLASPReliance on data layout
+ References
[REF-62] Mark Dowd, John McDonald and Justin Schuh. "The Art of Software Security Assessment". Chapter 6, "Structure Padding", Page 284. 1st Edition. Addison Wesley. 2006.
+ Content History
Submissions
Submission DateSubmitterOrganization
CLASP
Modifications
Modification DateModifierOrganization
2008-07-01Eric DalciCigital
updated Time_of_Introduction
2008-09-08CWE Content TeamMITRE
updated Applicable_Platforms, Common_Consequences, Relationships, Other_Notes, Taxonomy_Mappings
2009-03-10CWE Content TeamMITRE
updated Relationships
2009-10-29CWE Content TeamMITRE
updated Common_Consequences
2011-03-29CWE Content TeamMITRE
updated Common_Consequences
2011-06-01CWE Content TeamMITRE
updated Common_Consequences
2012-05-11CWE Content TeamMITRE
updated References, Relationships
2012-10-30CWE Content TeamMITRE
updated Potential_Mitigations
2014-06-23CWE Content TeamMITRE
updated Description, Other_Notes
2014-07-30CWE Content TeamMITRE
updated Demonstrative_Examples, Relationships
Previous Entry Names
Change DatePrevious Entry Name
2008-04-11Reliance on Data Layout

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Page Last Updated: January 18, 2018