Object Model Violation: Just One of Equals and Hashcode Defined
Draft Variant
Structure: Simple
Description
The product does not maintain equal hashcodes for equal objects.
Java objects are expected to obey a number of invariants related to equality. One of these invariants is that equal objects must have equal hashcodes. In other words, if a.equals(b) == true then a.hashCode() == b.hashCode().
Common Consequences 1
Scope: IntegrityOther
Impact: Other
If this invariant is not upheld, it is likely to cause trouble if objects of this class are stored in a collection. If the objects of the class in question are used as a key in a Hashtable or if they are inserted into a Map or Set, it is critical that equal objects have equal hashcodes.
Detection Methods 1
Automated Static AnalysisHigh
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.)Potential Mitigations 1
Phase: Implementation
Both Equals() and Hashcode() should be defined.
Applicable Platforms
Languages:
Java : Undetermined
Modes of Introduction
Implementation
Related Weaknesses
Taxonomy Mapping
- The CERT Oracle Secure Coding Standard for Java (2011)