CWE

Common Weakness Enumeration

A Community-Developed List of Software Weakness Types

CWE/SANS Top 25 Most Dangerous Software Errors
Home > CWE List > CWE- Individual Dictionary Definition (3.1)  
ID

CWE-597: Use of Wrong Operator in String Comparison

Weakness ID: 597
Abstraction: Variant
Structure: Simple
Status: Draft
Presentation Filter:
+ Description
The product uses the wrong operator when comparing a string, such as using "==" when the equals() method should be used instead.
+ Extended Description
In Java, using == or != to compare two strings for equality actually compares two objects for equality, not their values. Chances are good that the two references will never be equal. While this weakness often only affects program correctness, if the equality is used for a security decision, it could be leveraged to affect program security.
+ 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)
NatureTypeIDName
ChildOfBaseBase - a weakness that is described in an abstract fashion, but with sufficient details to infer specific methods for detection and prevention. More general than a Variant weakness, but more specific than a Class weakness.480Use of Incorrect Operator
ChildOfVariantVariant - a weakness that is described at a very low level of detail, typically limited to a specific language or technology. More specific than a Base weakness.595Comparison of Object References Instead of Object Contents
+ Relevant to the view "Development Concepts" (CWE-699)
NatureTypeIDName
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.133String Errors
ChildOfBaseBase - a weakness that is described in an abstract fashion, but with sufficient details to infer specific methods for detection and prevention. More general than a Variant weakness, but more specific than a Class weakness.480Use of Incorrect Operator
ChildOfVariantVariant - a weakness that is described at a very low level of detail, typically limited to a specific language or technology. More specific than a Base weakness.595Comparison of Object References Instead of Object Contents
+ 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
+ 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: Other

+ Demonstrative Examples

Example 1

In the example below, two Java String objects are declared and initialized with the same string values and an if statement is used to determine if the strings are equivalent.

(bad code)
Example Language: Java 
String str1 = new String("Hello");
String str2 = new String("Hello");
if (str1 == str2) {
System.out.println("str1 == str2");
}

However, the if statement will not be executed as the strings are compared using the "==" operator. For Java objects, such as String objects, the "==" operator compares object references, not object values. While the two String objects above contain the same string values, they refer to different object references, so the System.out.println statement will not be executed. To compare object values, the previous code could be modified to use the equals method:

(good code)
 
if (str1.equals(str2)) {
System.out.println("str1 equals str2");
}
+ Potential Mitigations

Phase: Implementation

Use equals() to compare strings.

Effectiveness: High

+ 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.
NatureTypeIDName
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.847CERT Java Secure Coding Section 02 - Expressions (EXP)
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.998SFP Secondary Cluster: Glitch in Computation
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
CERT Java Secure CodingEXP03-JDo not use the equality operators when comparing values of boxed primitives
CERT Java Secure CodingEXP03-JDo not use the equality operators when comparing values of boxed primitives
CERT Perl Secure CodingEXP35-PLCWE More SpecificUse the correct operator type for comparing values
Software Fault PatternsSFP1Glitch in computation
+ References
[REF-62] Mark Dowd, John McDonald and Justin Schuh. "The Art of Software Security Assessment". Chapter 6, "Typos", Page 289. 1st Edition. Addison Wesley. 2006.
+ Content History
Modifications
Modification DateModifierOrganization
2008-07-01Eric DalciCigital
updated Potential_Mitigations, Time_of_Introduction
2008-09-08CWE Content TeamMITRE
updated Description, Relationships
2008-10-14CWE Content TeamMITRE
updated Relationships
2009-05-27CWE Content TeamMITRE
updated Demonstrative_Examples
2011-03-29CWE Content TeamMITRE
updated Demonstrative_Examples, Description, Potential_Mitigations
2011-06-01CWE Content TeamMITRE
updated Common_Consequences, Relationships, Taxonomy_Mappings
2012-05-11CWE Content TeamMITRE
updated Demonstrative_Examples, References, Relationships, Taxonomy_Mappings
2014-07-30CWE Content TeamMITRE
updated Relationships, Taxonomy_Mappings
2017-11-08CWE Content TeamMITRE
updated Taxonomy_Mappings
Previous Entry Names
Change DatePrevious Entry Name
2008-04-11Erroneous String Compare

More information is available — Please select a different filter.
Page Last Updated: March 29, 2018