{"@ID": "595", "@Name": "Comparison of Object References Instead of Object Contents", "@Abstraction": "Variant", "@Structure": "Simple", "@Status": "Incomplete", "Description": "The product compares object references instead of the contents of the objects themselves, preventing it from detecting equivalent objects.", "Extended_Description": "For example, in Java, comparing objects using == usually produces deceptive results, since the == operator compares object references rather than values; often, this means that using == for strings is actually comparing the strings' references, not their values.", "Related_Weaknesses": {"Related_Weakness": {"@Nature": "ChildOf", "@CWE_ID": "1025", "@View_ID": "1000", "@Ordinal": "Primary"}}, "Weakness_Ordinalities": {"Weakness_Ordinality": {"Ordinality": "Primary"}}, "Applicable_Platforms": {"Language": [{"@Class": "Not Language-Specific", "@Prevalence": "Undetermined"}, {"@Name": "Java", "@Prevalence": "Undetermined"}, {"@Name": "JavaScript", "@Prevalence": "Undetermined"}, {"@Name": "PHP", "@Prevalence": "Undetermined"}, {"@Name": "Python", "@Prevalence": "Undetermined"}]}, "Modes_Of_Introduction": {"Introduction": {"Phase": "Implementation"}}, "Common_Consequences": {"Consequence": {"Scope": "Other", "Impact": "Varies by Context", "Note": "This weakness can lead to erroneous results that can cause unexpected application behaviors."}}, "Detection_Methods": {"Detection_Method": {"@Detection_Method_ID": "DM-14", "Method": "Automated Static Analysis", "Description": "Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect \"sources\" (origins of input) with \"sinks\" (destinations where the data interacts with external components, a lower layer such as the OS, etc.)", "Effectiveness": "High"}}, "Potential_Mitigations": {"Mitigation": {"Phase": "Implementation", "Description": "In Java, use the equals() method to compare objects instead of the == operator. If using ==, it is important for performance reasons that your objects are created by a static factory, not by a constructor."}}, "Demonstrative_Examples": {"Demonstrative_Example": [{"@Demonstrative_Example_ID": "DX-60", "Intro_Text": "In the example below, two Java String objects are declared and initialized with the same string values. An if statement is used to determine if the strings are equivalent.", "Example_Code": [{"@Nature": "Bad", "@Language": "Java", "xhtml:div": {"xhtml:br": [null, null], "xhtml:div": {"@style": "margin-left:1em;", "#text": "System.out.println(\"str1 == str2\");"}, "#text": "String str1 = new String(\"Hello\");String str2 = new String(\"Hello\");if (str1 == str2) {}"}, "#text_blocks": ["String str1 = new String(\"Hello\");", "String str2 = new String(\"Hello\");", "if (str1 == str2) {", "System.out.println(\"str1 == str2\");", "}"]}, {"@Nature": "Good", "@Language": "Java", "xhtml:div": {"xhtml:div": {"@style": "margin-left:1em;", "#text": "System.out.println(\"str1 equals str2\");"}, "#text": "if (str1.equals(str2)) {}"}, "#text_blocks": ["if (str1.equals(str2)) {", "System.out.println(\"str1 equals str2\");", "}"]}], "Body_Text": "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:"}, {"Intro_Text": "In the following Java example, two BankAccount objects are compared in the isSameAccount method using the == operator.", "Example_Code": [{"@Nature": "Bad", "@Language": "Java", "xhtml:div": {"xhtml:div": {"@style": "margin-left:1em;", "#text": "return accountA == accountB;"}, "#text": "public boolean isSameAccount(BankAccount accountA, BankAccount accountB) {}"}, "#text_blocks": ["public boolean isSameAccount(BankAccount accountA, BankAccount accountB) {", "return accountA == accountB;", "}"]}, {"@Nature": "Good", "@Language": "Java", "xhtml:div": {"xhtml:div": {"@style": "margin-left:1em;", "#text": "return accountA.equals(accountB);"}, "#text": "public boolean isSameAccount(BankAccount accountA, BankAccount accountB) {}"}, "#text_blocks": ["public boolean isSameAccount(BankAccount accountA, BankAccount accountB) {", "return accountA.equals(accountB);", "}"]}], "Body_Text": ["Using the == operator to compare objects may produce incorrect or deceptive results by comparing object references rather than values. The equals() method should be used to ensure correct results or objects should contain a member variable that uniquely identifies the object.", "The following example shows the use of the equals() method to compare the BankAccount objects and the next example uses a class get method to retrieve the bank account number that uniquely identifies the BankAccount object to compare the objects."]}]}, "Taxonomy_Mappings": {"Taxonomy_Mapping": [{"@Taxonomy_Name": "The CERT Oracle Secure Coding Standard for Java (2011)", "Entry_ID": "EXP02-J", "Entry_Name": "Use the two-argument Arrays.equals() method to compare the contents of arrays"}, {"@Taxonomy_Name": "The CERT Oracle Secure Coding Standard for Java (2011)", "Entry_ID": "EXP02-J", "Entry_Name": "Use the two-argument Arrays.equals() method to compare the contents of arrays"}, {"@Taxonomy_Name": "The CERT Oracle Secure Coding Standard for Java (2011)", "Entry_ID": "EXP03-J", "Entry_Name": "Do not use the equality operators when comparing values of boxed primitives"}, {"@Taxonomy_Name": "OpenSSF Secure Coding Guide for Python", "Entry_ID": "pyscg-0033", "Entry_Name": "Implement Comparisons by Value Rather Than Reference"}]}, "References": {"Reference": [{"@External_Reference_ID": "REF-954"}, {"@External_Reference_ID": "REF-1534"}, {"@External_Reference_ID": "REF-1541", "@Section": "08 Coding Standards"}]}, "Mapping_Notes": {"Usage": "Allowed", "Rationale": "This CWE entry is at the Variant level of abstraction, which is a preferred level of abstraction for mapping to the root causes of vulnerabilities.", "Comments": "Carefully read both the name and description to ensure that this mapping is an appropriate fit. Do not try to 'force' a mapping to a lower-level Base/Variant simply to comply with this preferred level of abstraction.", "Reasons": {"Reason": {"@Type": "Acceptable-Use"}}}, "Content_History": {"Submission": {"Submission_Name": "CWE Content Team", "Submission_Organization": "MITRE", "Submission_Date": "2006-12-15", "Submission_Version": "Draft 5", "Submission_ReleaseDate": "2006-12-15"}, "Modification": [{"Modification_Name": "Sean Eidemiller", "Modification_Organization": "Cigital", "Modification_Date": "2008-07-01", "Modification_Version": "1.0", "Modification_ReleaseDate": "2008-09-09", "Modification_Comment": "added/updated demonstrative examples"}, {"Modification_Name": "Eric Dalci", "Modification_Organization": "Cigital", "Modification_Date": "2008-07-01", "Modification_Version": "1.0", "Modification_ReleaseDate": "2008-09-09", "Modification_Comment": "updated Time_of_Introduction"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2008-09-08", "Modification_Version": "1.0", "Modification_ReleaseDate": "2008-09-09", "Modification_Comment": "updated Description, Relationships, Other_Notes"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2009-05-27", "Modification_Version": "1.4", "Modification_ReleaseDate": "2009-05-27", "Modification_Comment": "updated Name"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2010-12-13", "Modification_Version": "1.11", "Modification_ReleaseDate": "2010-12-13", "Modification_Comment": "updated Demonstrative_Examples"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2011-06-01", "Modification_Version": "1.13", "Modification_ReleaseDate": "2011-06-01", "Modification_Comment": "updated Common_Consequences, Relationships, Taxonomy_Mappings"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2012-05-11", "Modification_Version": "2.2", "Modification_ReleaseDate": "2012-05-15", "Modification_Comment": "updated Common_Consequences, Demonstrative_Examples, Relationships, Taxonomy_Mappings"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2012-10-30", "Modification_Version": "2.3", "Modification_ReleaseDate": "2012-10-30", "Modification_Comment": "updated Potential_Mitigations"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2014-06-23", "Modification_Version": "2.7", "Modification_ReleaseDate": "2014-06-23", "Modification_Comment": "updated Applicable_Platforms, Common_Consequences"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2014-07-30", "Modification_Version": "2.8", "Modification_ReleaseDate": "2014-07-31", "Modification_Comment": "updated Relationships"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2018-03-27", "Modification_Version": "3.1", "Modification_ReleaseDate": "2018-03-27", "Modification_Comment": "updated Applicable_Platforms, Common_Consequences, Description, Other_Notes, Potential_Mitigations, References, Relationships, Type"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2019-01-03", "Modification_Version": "3.2", "Modification_ReleaseDate": "2019-01-03", "Modification_Comment": "updated Relationships, Taxonomy_Mappings"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2020-02-24", "Modification_Version": "4.0", "Modification_ReleaseDate": "2020-02-24", "Modification_Comment": "updated Relationships"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2020-08-20", "Modification_Version": "4.2", "Modification_ReleaseDate": "2020-08-20", "Modification_Comment": "updated Relationships"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2021-03-15", "Modification_Version": "4.4", "Modification_ReleaseDate": "2021-03-15", "Modification_Comment": "updated Demonstrative_Examples"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2023-01-31", "Modification_Version": "4.10", "Modification_ReleaseDate": "2023-01-31", "Modification_Comment": "updated Description"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2023-04-27", "Modification_Version": "4.11", "Modification_ReleaseDate": "2023-04-27", "Modification_Comment": "updated Detection_Factors, Relationships"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2023-06-29", "Modification_Version": "4.12", "Modification_ReleaseDate": "2023-06-29", "Modification_Comment": "updated Mapping_Notes"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2025-04-03", "Modification_Version": "4.17", "Modification_ReleaseDate": "2025-04-03", "Modification_Comment": "updated Demonstrative_Examples"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2025-09-09", "Modification_Version": "4.18", "Modification_ReleaseDate": "2025-09-09", "Modification_Comment": "updated References"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2025-12-11", "Modification_Version": "4.19", "Modification_ReleaseDate": "2025-12-11", "Modification_Comment": "updated Weakness_Ordinalities"}, {"Modification_Name": "CWE Content Team", "Modification_Organization": "MITRE", "Modification_Date": "2026-10-28", "Modification_Version": "5.0", "Modification_ReleaseDate": "2026-10-28", "Modification_Comment": "updated Applicable_Platforms, References, Relationships, Taxonomy_Mappings"}], "Previous_Entry_Name": [{"@Date": "2008-04-11", "#text": "Incorrect Object Comparison: Syntactic"}, {"@Date": "2009-05-27", "#text": "Incorrect Syntactic Object Comparison"}]}, "entry_type": "Weakness"}