COMMON WEAKNESS ENUMERATIONDraft

CWE-188

Reliance on Data/Memory Layout

The product makes invalid assumptions about how protocol data or memory is organized at a lower level, resulting in unintended program behavior.

Abstraction

Base

Structure

Simple

Likelihood of Exploit

Low

Understand the problem

What is the problem?

The product 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, in-memory organization of data may change 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.

Root cause

How and when does the problem arise?

Lifecycle phase

Implementation

Risk

What does successful exploitation lead to?

Modify MemoryRead Memory

Affected security scopes: Integrity, Confidentiality

Can result in unintended modifications or exposure of sensitive memory.

Defence

How is it prevented and fixed?

Implementation · Architecture and Design

Defence to apply across several lifecycle phases

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

Architecture and Design

Architecture and design approach

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

Testing

Testing and verification approach

Detail
Testing: Test that the implementation properly handles each case in the protocol grammar.

Verification

How is it detected?

Fuzzing

High
Fuzz testing (fuzzing) is a powerful technique for generating large numbers of diverse inputs - either randomly or algorithmically - and dynamically invoking the code with those inputs. Even with random inputs, it is often capable of generating unexpected results such as crashes, memory corruption, or resource consumption. Fuzzing effectively produces repeatable test cases that clearly indicate bugs, which helps developers to diagnose the issues.

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.