CWE-480 Base Draft Low likelihood

Use of Incorrect Operator

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

Definition

What is CWE-480?

This vulnerability occurs when a developer mistakenly uses the wrong operator in their code, leading to unintended and potentially insecure logic.
This flaw is almost always a simple typographical error, like using a single equals sign (=) for comparison instead of a double (== or ===), or confusing logical AND (&&) with OR (||). These small mistakes can drastically change how a program behaves, bypassing critical security checks, granting unintended access, or corrupting data. To prevent this, developers should adopt defensive coding practices like using linters and static analysis tools that can catch these errors automatically. Code reviews are also essential for spotting incorrect operators, especially in security-critical sections like authentication, authorization, and input validation routines.
Real-world impact

Real-world CVEs caused by CWE-480

  • CVE-2022-3979

    Chain: data visualization program written in PHP uses the "!=" operator instead of the type-strict "!==" operator (CWE-480) when validating hash values, potentially leading to an incorrect type conversion (CWE-704)

  • CVE-2021-3116

    Chain: Python-based HTTP Proxy server uses the wrong boolean operators (CWE-480) causing an incorrect comparison (CWE-697) that identifies an authN failure if all three conditions are met instead of only one, allowing bypass of the proxy authentication (CWE-1390)

How attackers exploit it

Step-by-step attacker path

  1. 1

    The following C/C++ and C# examples attempt to validate an int input parameter against the integer value 100.

  2. 2

    However, the expression to be evaluated in the if statement uses the assignment operator "=" rather than the comparison operator "==". The result of using the assignment operator instead of the comparison operator causes the int variable to be reassigned locally and the expression in the if statement will always evaluate to the value on the right hand side of the expression. This will result in the input value not being properly validated, which can cause unexpected results.

  3. 3

    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.

  4. 4

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

  5. 5

    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 C

The following C/C++ and C# examples attempt to validate an int input parameter against the integer value 100.

Vulnerable C 
int isValid(int value) {
  	if (value=100) {
  		printf("Value is valid\n");
  		return(1);
  	}
  	printf("Value is not valid\n");
  	return(0);
  }
Secure code example

Secure Verilog

A fix to this issue is to only change the privilege level of the processor when both checks are satisfied, i.e., the request has enough privileges (i.e., debug_mode_q is enabled) and the password checking is successful (i.e., umode_i is enabled) [REF-1378].

Secure Verilog 
module csr_regfile #(
 ...

```
   // check that we actually want to enter debug depending on the privilege level we are currently in
   unique case (priv_lvl_o)
  	 riscv::PRIV_LVL_M: begin
  		 debug_mode_d = dcsr_q.ebreakm;
 ...
  	 riscv::PRIV_LVL_U: begin
  		 debug_mode_d = dcsr_q.ebreaku;
 ...
   assign priv_lvl_o = 
```
(debug_mode_q && umode_i) ? riscv::PRIV_LVL_M : priv_lvl_q;** 
   ...

```
   debug_mode_q <= debug_mode_d;
 ...
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-480

  • Architecture Use safe-by-default frameworks and APIs that prevent the unsafe pattern from being expressible.
  • Implementation Validate input at trust boundaries; use allowlists, not denylists.
  • Implementation Apply the principle of least privilege to credentials, file paths, and runtime permissions.
  • Testing Cover this weakness in CI: SAST rules + targeted unit tests for the data flow.
  • Operation Monitor logs for the runtime signals listed in the next section.
Detection signals

How to detect CWE-480

Automated Static Analysis

This weakness can be found easily using static analysis. However in some cases an operator might appear to be incorrect, but is actually correct and reflects unusual logic within the program.

Manual Static Analysis

This weakness can be found easily using static analysis. However in some cases an operator might appear to be incorrect, but is actually correct and reflects unusual logic within the program.

Plexicus auto-fix

Plexicus auto-detects CWE-480 and opens a fix PR in under 60 seconds.

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Frequently asked questions

Frequently asked questions

What is CWE-480?

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

How serious is CWE-480?

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-480?

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

How can I prevent CWE-480?

Use safe-by-default frameworks, validate untrusted input at trust boundaries, and apply the principle of least privilege. Cover the data-flow signature in CI with SAST.

How does Plexicus detect and fix CWE-480?

Plexicus's SAST engine matches the data-flow signature for CWE-480 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-480?

MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/480.html. You can also reference OWASP and NIST documentation for adjacent guidance.

Related weaknesses

Weaknesses related to CWE-480

CWE-670 Parent

Always-Incorrect Control Flow Implementation

This weakness occurs when a section of code is structured in a way that always executes incorrectly, regardless of input or conditions.…

CWE-483 Sibling

Incorrect Block Delimitation

This vulnerability occurs when a developer fails to use explicit braces or delimiters to group multiple statements within a block, leading…

CWE-484 Sibling

Omitted Break Statement in Switch

This vulnerability occurs when a developer forgets to include a 'break' statement inside a switch-case block. Without it, the code…

CWE-617 Sibling

Reachable Assertion

A reachable assertion occurs when an attacker can trigger an assert() statement or similar debugging check, causing the application to…

CWE-698 Sibling

Execution After Redirect (EAR)

Execution After Redirect (EAR) occurs when a web application sends a redirect response to a user's browser but continues to run…

CWE-783 Sibling

Operator Precedence Logic Error

This vulnerability occurs when a developer writes a conditional expression where the intended logic is broken due to misunderstanding or…

CWE-481 Child

Assigning instead of Comparing

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

CWE-482 Child

Comparing instead of Assigning

This vulnerability occurs when a developer accidentally uses a comparison operator (like '==') where an assignment operator (like '=') was…

CWE-597 Child

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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