CWE

Assigning instead of Comparing

ID: 481		Date: (C)2012-05-14   (M)2022-10-10
Type: weakness		Status: DRAFT
Abstraction Type: Variant

Description

The code uses an operator for assignment when the intention was to perform a comparison.

Extended Description

In many languages the compare statement is very close in appearance to the assignment statement and are often confused. This bug is generally the result of a typo and usually causes obvious problems with program execution. If the comparison is in an if statement, the if statement will usually evaluate the value of the right-hand side of the predicate.

Likelihood of Exploit: Low

Applicable Platforms
Language: C
Language: C++
Language: Java
Language: .NET

Time Of Introduction

• Implementation

Common Consequences

Scope	Technical Impact	Notes
Other	Alter execution logic

Detection Methods
None

Potential Mitigations

Phase	Strategy	Description	Effectiveness	Notes
Testing		Many IDEs and static analysis products will detect this problem.
Implementation		Place constants on the left. If one attempts to assign a constant with a variable, the compiler will of course produce an error.

Relationships

Related CWE	Type	View	Chain
CWE-481 ChildOf CWE-885	Category	CWE-888

Demonstrative Examples   (Details)

1. In this example, we show how assigning instead of comparing can impact code when values are being passed by reference instead of by value. Consider a scenario in which a string is being processed from user input. Assume the string has already been formatted such that different user inputs are concatenated with the colon character. When the processString function is called, the test for the colon character will result in an insertion of the colon character instead, adding new input separators. Since the string was passed by reference, the data sentinels will be inserted in the original string (CWE-464), and further processing of the inputs will be altered, possibly malformed..
2. The following C/C++ and C# examples attempt to validate an int input parameter against the integer value 100. (Demonstrative Example Id DX-102)
3. The following Java example attempts to perform some processing based on the boolean value of the input parameter. However, the expression to be evaluated in the if statement uses the assignment operator "=" rather than the comparison operator "==". As with the previous examples, the variable will be reassigned locally and the expression in the if statement will evaluate to true and unintended processing may occur.

White Box Definitions
None

Black Box Definitions
None

Taxynomy Mappings

Taxynomy	Id	Name	Fit
CLASP		Assigning instead of comparing

References:

1. Mark Dowd John McDonald Justin Schuh .The Art of Software Security Assessment 1st Edition. Addison Wesley. Section:'Chapter 6, "Typos", Page 289.'. Published on 2006.