CWE-188: Reliance on Data/Memory Layout

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.

Code Examples & CVEs

Demonstrative Examples

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.

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.

BadC

void example() {char a;char b;*(&a + 1) = 0;}

Source-backed guidance

Additional facts reviewed against primary or authoritative security sources.

Verify controls for CWE-188 with SSDF evidence

Use NIST SSDF verification and vulnerability-response practices to detect CWE-188, Reliance on Data/Memory Layout, throughout the product lifecycle. Derive review questions, static or dynamic checks, and negative tests from the CWE's causal behavior; define the components and lifecycle stages each check covers; and retain findings with enough evidence to distinguish the root cause from symptoms and impacts. Track escapes and false negatives, then improve the verification plan after every confirmed occurrence.

NIST SP 800-218 Secure Software Development Framework — National Institute of Standards and Technology

Address Reliance on Data/Memory Layout during Implementation

MITRE associates mitigation with Implementation, Architecture and Design, and Testing; documented detection approaches include Fuzzing, and Automated Dynamic Analysis; recorded impacts include Modify Memory, and Read Memory. Use these source-defined anchors to turn CWE-188 into implementation, review, and verification checks for the affected component.

CWE-188: Reliance on Data/Memory Layout — MITRE CWE

Triage CWE-188 against known exploitation evidence

Use CISA's Known Exploited Vulnerabilities catalog to test whether a vulnerability mapped to CWE-188, Reliance on Data/Memory Layout, has evidence of exploitation in the wild. Confirm the CVE-to-CWE root-cause mapping independently before attaching the example, then capture the affected product, required action, and remediation deadline. A missing KEV match is not evidence that the weakness is unexploited, and a KEV entry must not be generalized to every occurrence of this CWE.

Known Exploited Vulnerabilities Catalog — Cybersecurity and Infrastructure Security Agency

Apply precise root-cause mapping to CWE-188

Apply MITRE's full root-cause mapping guidance when using CWE-188, Reliance on Data/Memory Layout. Separate weakness language from attacker prerequisites and technical impact, check the entry's abstraction and vulnerability-mapping notes, and prefer the most specific Base or Variant supported by the evidence. Record the rejected alternatives and require an independent review before the mapping is used for remediation trends or program metrics.

CVE to CWE Root Cause Mapping Guidance — MITRE CWE

Validate CWE-188 with root-cause mapping checks

Apply MITRE's root-cause mapping quick tips to CWE-188, Reliance on Data/Memory Layout. Confirm the finding describes the causal weakness rather than an impact or attack pattern, compare the abstraction and mapping notes with plausible alternatives, and have a second reviewer challenge the selection. Preserve the evidence and reasoning so recurring defects can be measured against one consistent identifier.

CVE to CWE Root Cause Mapping Quick Tips — MITRE CWE

Frequently Asked Questions

What is CWE-188: Reliance on Data/Memory Layout?+

CWE-188: Reliance on Data/Memory Layout is a Common Weakness Enumeration (CWE) entry maintained by MITRE. The product makes invalid assumptions about how protocol data or memory is organized at a lower level, resulting in unintended program behavior. 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.

What are the security consequences of Reliance on Data/Memory Layout?+

If exploited, CWE-188 (Reliance on Data/Memory Layout) it can compromise Integrity and Confidentiality, leading to outcomes such as Modify Memory and Read Memory.

How do you prevent or mitigate Reliance on Data/Memory Layout?+

Recommended mitigations for CWE-188 include: In flat address space situations, never allow computing memory addresses as offsets from another memory address. Fully specify protocol layout unambiguously, providing a structured grammar (e.g., a compilable yacc grammar). Testing: Test that the implementation properly handles each case in the protocol grammar.

Which programming languages are affected by Reliance on Data/Memory Layout?+

CWE-188 commonly affects C, C++ and Not Language-Specific. Note that weaknesses are often language-agnostic patterns, so secure coding practices apply broadly.

What is the difference between a CWE and a CVE?+

A CWE (Common Weakness Enumeration) like CWE-188 describes a category of software weakness — the underlying flaw type. A CVE (Common Vulnerabilities and Exposures) identifies a specific, real-world vulnerability in a particular product. In short, a CWE is the kind of mistake, and a CVE is an instance of that mistake being found in software.

CWE-188: Reliance on Data/Memory Layout

Extended Description

Technical Details

Applicable To

Security Consequences

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Impact

Mitigation Strategies

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Description

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Detection Methods

Code Examples & CVEs

Demonstrative Examples

CWE Relationships

Parent Weaknesses

Source-backed guidance

Verify controls for CWE-188 with SSDF evidence

Address Reliance on Data/Memory Layout during Implementation

Triage CWE-188 against known exploitation evidence

Apply precise root-cause mapping to CWE-188

Validate CWE-188 with root-cause mapping checks

Frequently Asked Questions

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