CWE-482 Variant Draft Low likelihood

Comparing instead of Assigning

This vulnerability occurs when a developer accidentally uses a comparison operator (like '==') where an assignment operator (like '=') was intended, creating a logic error instead of setting a value.

Definition

What is CWE-482?

This vulnerability occurs when a developer accidentally uses a comparison operator (like '==') where an assignment operator (like '=') was intended, creating a logic error instead of setting a value.
This common coding mistake happens because assignment and comparison operators look very similar in many programming languages. For example, using `if (x = 5)` instead of `if (x == 5)` assigns the value 5 to `x` and then evaluates the assignment's result as the condition, which is often always true, breaking the intended program logic. To prevent this, developers should adopt defensive coding habits like placing constants on the left side in comparisons (e.g., `if (5 == x)`), which would cause a compilation error if written incorrectly as `if (5 = x)`. Modern compilers and linters often flag this pattern with warnings like "possible unintended assignment," which should always be investigated and corrected.
Real-world impact

Real-world CVEs caused by CWE-482

No public CVE references are linked to this CWE in MITRE's catalog yet.

How attackers exploit it

Step-by-step attacker path

  1. 1

    The following example demonstrates the weakness.

  2. 2

    The following C/C++ example shows a simple implementation of a stack that includes methods for adding and removing integer values from the stack. The example uses pointers to add and remove integer values to the stack array variable.

  3. 3

    The push method includes an expression to assign the integer value to the location in the stack pointed to by the pointer variable.

  4. 4

    However, this expression uses the comparison operator "==" rather than the assignment operator "=". The result of using the comparison operator instead of the assignment operator causes erroneous values to be entered into the stack and can cause unexpected results.

Vulnerable code example

Vulnerable Java

The following example demonstrates the weakness.

Vulnerable Java 
void called(int foo) {
  	foo==1;
  	if (foo==1) System.out.println("foo\n");
  }
  int main() {
  		called(2);
  		return 0;
  }
Secure code example

Secure pseudo

Secure pseudo 
// Validate, sanitize, or use a safe API before reaching the sink.
function handleRequest(input) {
  const safe = validateAndEscape(input);
  return executeWithGuards(safe);
}
What changed: the unsafe sink is replaced (or the input is validated/escaped) so the same payload no longer triggers the weakness.
Prevention checklist

How to prevent CWE-482

  • Testing Many IDEs and static analysis products will detect this problem.
Detection signals

How to detect CWE-482

Automated Static Analysis High

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.)

Plexicus auto-fix

Plexicus auto-detects CWE-482 and opens a fix PR in under 60 seconds.

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Frequently asked questions

Frequently asked questions

What is CWE-482?

This vulnerability occurs when a developer accidentally uses a comparison operator (like '==') where an assignment operator (like '=') was intended, creating a logic error instead of setting a value.

How serious is CWE-482?

MITRE rates the likelihood of exploit as Low — exploitation is uncommon, but the weakness should still be fixed when discovered.

What languages or platforms are affected by CWE-482?

MITRE lists the following affected platforms: C, C++.

How can I prevent CWE-482?

Many IDEs and static analysis products will detect this problem.

How does Plexicus detect and fix CWE-482?

Plexicus's SAST engine matches the data-flow signature for CWE-482 on every commit. When a match is found, our Codex Remedium agent opens a fix PR with the corrected code, tests, and a one-line summary for the reviewer.

Where can I learn more about CWE-482?

MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/482.html. You can also reference OWASP and NIST documentation for adjacent guidance.

Related weaknesses

Weaknesses related to CWE-482

CWE-480 Parent

Use of Incorrect Operator

This vulnerability occurs when a developer mistakenly uses the wrong operator in their code, leading to unintended and potentially…

CWE-481 Sibling

Assigning instead of Comparing

This flaw occurs when a developer accidentally uses the assignment operator (=) instead of the comparison operator (== or ===). The code…

CWE-597 Sibling

Use of Wrong Operator in String Comparison

This vulnerability occurs when a developer incorrectly compares string values, typically by using reference equality operators (like == or…

Resources

Further reading

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