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-241: Improper Handling of Unexpected Data Type

Weakness ID: 241
Abstraction: Base
Status: Draft
Presentation Filter:
+ Description

Description Summary

The software does not handle or incorrectly handles when a particular element is not the expected type, e.g. it expects a digit (0-9) but is provided with a letter (A-Z).
+ Time of Introduction
  • Architecture and Design
  • Implementation
+ Applicable Platforms

Languages

All

+ Common Consequences
ScopeEffect
Integrity
Other

Technical Impact: Varies by context; Unexpected state

+ Observed Examples
ReferenceDescription
FTP server crash via PORT command with non-numeric character.
Anti-virus product has assert error when line length is non-numeric.
+ Potential Mitigations

Phase: Implementation

Strategy: Input Validation

Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a whitelist of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.

When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue."

Do not rely exclusively on looking for malicious or malformed inputs (i.e., do not rely on a blacklist). A blacklist is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, blacklists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.

Phase: Implementation

Strategy: Input Validation

Inputs should be decoded and canonicalized to the application's current internal representation before being validated (CWE-180). Make sure that the application does not decode the same input twice (CWE-174). Such errors could be used to bypass whitelist validation schemes by introducing dangerous inputs after they have been checked.

+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfWeakness ClassWeakness Class228Improper Handling of Syntactically Invalid Structure
Development Concepts (primary)699
Research Concepts (primary)1000
ChildOfCategoryCategory743CERT C Secure Coding Section 09 - Input Output (FIO)
Weaknesses Addressed by the CERT C Secure Coding Standard (primary)734
ChildOfCategoryCategory877CERT C++ Secure Coding Section 09 - Input Output (FIO)
Weaknesses Addressed by the CERT C++ Secure Coding Standard (primary)868
ChildOfCategoryCategory993SFP Secondary Cluster: Incorrect Input Handling
Software Fault Pattern (SFP) Clusters (primary)888
+ Research Gaps

Probably under-studied.

+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
PLOVERWrong Data Type
CERT C Secure CodingFIO37-CDo not assume character data has been read
CERT C++ Secure CodingFIO37-CPPDo not assume character data has been read
+ Content History
Submissions
Submission DateSubmitterOrganizationSource
PLOVERExternally Mined
Modifications
Modification DateModifierOrganizationSource
2008-07-01Eric DalciCigitalExternal
updated Potential_Mitigations, Time_of_Introduction
2008-09-08CWE Content TeamMITREInternal
updated Relationships, Taxonomy_Mappings
2008-11-24CWE Content TeamMITREInternal
updated Relationships, Taxonomy_Mappings
2009-03-10CWE Content TeamMITREInternal
updated Description, Name
2009-07-27CWE Content TeamMITREInternal
updated Potential_Mitigations
2009-10-29CWE Content TeamMITREInternal
updated Description
2011-03-29CWE Content TeamMITREInternal
updated Potential_Mitigations
2011-06-01CWE Content TeamMITREInternal
updated Common_Consequences
2011-06-27CWE Content TeamMITREInternal
updated Common_Consequences
2011-09-13CWE Content TeamMITREInternal
updated Relationships, Taxonomy_Mappings
2012-05-11CWE Content TeamMITREInternal
updated Relationships
2012-10-30CWE Content TeamMITREInternal
updated Potential_Mitigations
2014-07-30CWE Content TeamMITREInternal
updated Relationships
Previous Entry Names
Change DatePrevious Entry Name
2008-04-11Wrong Data Type
2009-03-10Failure to Handle Wrong Data Type

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Page Last Updated: May 05, 2017