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-242: Use of Inherently Dangerous Function

Weakness ID: 242
Abstraction: Base
Structure: Simple
Status: Draft
Presentation Filter:
+ Description
The program calls a function that can never be guaranteed to work safely.
+ Extended Description
Certain functions behave in dangerous ways regardless of how they are used. Functions in this category were often implemented without taking security concerns into account. The gets() function is unsafe because it does not perform bounds checking on the size of its input. An attacker can easily send arbitrarily-sized input to gets() and overflow the destination buffer. Similarly, the >> operator is unsafe to use when reading into a statically-allocated character array because it does not perform bounds checking on the size of its input. An attacker can easily send arbitrarily-sized input to the >> operator and overflow the destination buffer.
+ 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
MemberOfCategoryCategory1006Bad Coding Practices
+ 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
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
Other

Technical Impact: Varies by Context

+ Likelihood Of Exploit
High
+ Demonstrative Examples

Example 1

The code below calls gets() to read information into a buffer.

(bad code)
Example Language:
char buf[BUFSIZE];
gets(buf);

The gets() function in C is inherently unsafe.

Example 2

The code below calls the gets() function to read in data from the command line.

(bad code)
Example Language:
char buf[24];
printf("Please enter your name and press <Enter>\n");
gets(buf);
...
}

However, the programmer uses the function gets() which is inherently unsafe because it blindly copies all input from STDIN to the buffer without checking size. This allows the user to provide a string that is larger than the buffer size, resulting in an overflow condition.

+ Potential Mitigations

Phases: Implementation; Requirements

Ban the use of dangerous functions. Use their safe equivalent.

Phase: Testing

Use grep or static analysis tools to spot usage of dangerous functions.
+ Weakness Ordinalities
OrdinalityDescription
Primary
(where the weakness exists independent of other weaknesses)
+ 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.
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
7 Pernicious KingdomsDangerous Functions
CERT C Secure CodingPOS33-CCWE More AbstractDo not use vfork()
Software Fault PatternsSFP3Use of an improper API
+ References
[REF-194] Herbert Schildt. "Herb Schildt's C++ Programming Cookbook". Chapter 5. Working with I/O. McGraw-Hill Osborne Media. 2008-04-28.
[REF-7] Michael Howard and David LeBlanc. "Writing Secure Code". Chapter 5, "gets and fgets" Page 163. 2nd Edition. Microsoft Press. 2002-12-04. <https://www.microsoft.com/mspress/books/toc/5957.aspx>.
+ Content History
Submissions
Submission DateSubmitterOrganization
7 Pernicious Kingdoms
Modifications
Modification DateModifierOrganization
2008-07-01Sean EidemillerCigital
added/updated demonstrative examples
2008-07-01Eric DalciCigital
updated Potential_Mitigations
2008-09-08CWE Content TeamMITRE
updated Applicable_Platforms, Relationships, Other_Notes, Taxonomy_Mappings, Type, Weakness_Ordinalities
2008-11-24CWE Content TeamMITRE
updated Relationships, Taxonomy_Mappings
2009-10-29CWE Content TeamMITRE
updated Description, Other_Notes, References
2010-02-16CWE Content TeamMITRE
updated Demonstrative_Examples, References, Relationships
2010-04-05CWE Content TeamMITRE
updated Relationships
2011-06-01CWE Content TeamMITRE
updated Common_Consequences
2011-06-27CWE Content TeamMITRE
updated Common_Consequences
2012-05-11CWE Content TeamMITRE
updated Relationships
2012-10-30CWE Content TeamMITRE
updated Potential_Mitigations
2014-07-30CWE Content TeamMITRE
updated Demonstrative_Examples, Relationships, Taxonomy_Mappings
2017-11-08CWE Content TeamMITRE
updated Causal_Nature, References, Relationships, Taxonomy_Mappings
Previous Entry Names
Change DatePrevious Entry Name
2008-01-30Dangerous Functions
2008-04-11Use of Inherently Dangerous Functions

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Page Last Updated: January 18, 2018