Common Weakness Enumeration

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CWE-128: Wrap-around Error

Wrap-around Error
Weakness ID: 128 (Weakness Base)Status: Incomplete
+ Description

Description Summary

Wrap around errors occur whenever a value is incremented past the maximum value for its type and therefore "wraps around" to a very small, negative, or undefined value.
+ Time of Introduction
  • Implementation
+ Applicable Platforms


C: (Often)

C++: (Often)

+ Common Consequences

Technical Impact: DoS: crash / exit / restart; DoS: resource consumption (CPU); DoS: resource consumption (memory); DoS: instability

This weakness will generally lead to undefined behavior and therefore crashes. In the case of overflows involving loop index variables, the likelihood of infinite loops is also high.

Technical Impact: Modify memory

If the value in question is important to data (as opposed to flow), simple data corruption has occurred. Also, if the wrap around results in other conditions such as buffer overflows, further memory corruption may occur.

Technical Impact: Execute unauthorized code or commands; Bypass protection mechanism

This weakness can sometimes trigger buffer overflows which can be used to execute arbitrary code. This is usually outside the scope of a program's implicit security policy.

+ Likelihood of Exploit


+ Demonstrative Examples

Example 1

The following image processing code allocates a table for images.

(Bad Code)
Example Language:
img_t table_ptr; /*struct containing img data, 10kB each*/
int num_imgs;
num_imgs = get_num_imgs();
table_ptr = (img_t*)malloc(sizeof(img_t)*num_imgs);

This code intends to allocate a table of size num_imgs, however as num_imgs grows large, the calculation determining the size of the list will eventually overflow (CWE-190). This will result in a very small list to be allocated instead. If the subsequent code operates on the list as if it were num_imgs long, it may result in many types of out-of-bounds problems (CWE-119).

+ Potential Mitigations

Requirements specification: The choice could be made to use a language that is not susceptible to these issues.

Phase: Architecture and Design

Provide clear upper and lower bounds on the scale of any protocols designed.

Phase: Implementation

Place sanity checks on all incremented variables to ensure that they remain within reasonable bounds.

+ Background Details

Due to how addition is performed by computers, if a primitive is incremented past the maximum value possible for its storage space, the system will not recognize this, and therefore increment each bit as if it still had extra space. Because of how negative numbers are represented in binary, primitives interpreted as signed may "wrap" to very large negative values.

+ Weakness Ordinalities
(where the weakness exists independent of other weaknesses)
+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfCategoryCategory189Numeric Errors
Development Concepts699
ChildOfWeakness ClassWeakness Class682Incorrect Calculation
Development Concepts (primary)699
Research Concepts (primary)1000
ChildOfCategoryCategory742CERT C Secure Coding Section 08 - Memory Management (MEM)
Weaknesses Addressed by the CERT C Secure Coding Standard (primary)734
ChildOfCategoryCategory876CERT C++ Secure Coding Section 08 - Memory Management (MEM)
Weaknesses Addressed by the CERT C++ Secure Coding Standard (primary)868
ChildOfCategoryCategory885SFP Cluster: Risky Values
Software Fault Pattern (SFP) Clusters (primary)888
CanPrecedeWeakness ClassWeakness Class119Improper Restriction of Operations within the Bounds of a Memory Buffer
Research Concepts1000
PeerOfWeakness BaseWeakness Base190Integer Overflow or Wraparound
Research Concepts1000
+ Relationship Notes

The relationship between overflow and wrap-around needs to be examined more closely, since several entries (including CWE-190) are closely related.

+ Causal Nature


+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
CLASPWrap-around error
CERT C Secure CodingMEM07-CEnsure that the arguments to calloc(), when multiplied, can be represented as a size_t
CERT C++ Secure CodingMEM07-CPPEnsure that the arguments to calloc(), when multiplied, can be represented as a size_t
+ References
[REF-17] Michael Howard, David LeBlanc and John Viega. "24 Deadly Sins of Software Security". "Sin 5: Buffer Overruns." Page 89. McGraw-Hill. 2010.
[REF-7] Mark Dowd, John McDonald and Justin Schuh. "The Art of Software Security Assessment". Chapter 6, "Signed Integer Boundaries", Page 220.. 1st Edition. Addison Wesley. 2006.
+ Content History
Submission DateSubmitterOrganizationSource
Externally Mined
Modification DateModifierOrganizationSource
updated Applicable_Platforms, Background_Details, Common_Consequences, Relationships, Relationship_Notes, Taxonomy_Mappings, Weakness_Ordinalities
updated Relationships, Taxonomy_Mappings
updated Common_Consequences, Relationships
updated Background_Details
updated Common_Consequences
updated Relationships, Taxonomy_Mappings
updated Common_Consequences, Demonstrative_Examples, References, Relationships
Page Last Updated: June 23, 2014