COMMON WEAKNESS ENUMERATIONDraft

CWE-783

Operator Precedence Logic Error

The product uses an expression in which operator precedence causes incorrect logic to be used.

Abstraction

Base

Structure

Simple

Likelihood of Exploit

Low

Understand the problem

What is the problem?

The product uses an expression in which operator precedence causes incorrect logic to be used.

Extended description

While often just a bug, operator precedence logic errors can have serious consequences if they are used in security-critical code, such as making an authentication decision.

Root cause

How and when does the problem arise?

Lifecycle phase

Implementation

Logic errors related to operator precedence may cause problems even during normal operation, so they are probably discovered quickly during the testing phase. If testing is incomplete or there is a strong reliance on manual review of the code, then these errors may not be discovered before the software is deployed.

Risk

What does successful exploitation lead to?

Varies by ContextUnexpected State

Affected security scopes: Confidentiality, Integrity, Availability

The consequences will vary based on the context surrounding the incorrect precedence. In a security decision, integrity or confidentiality are the most likely results. Otherwise, a crash may occur due to the software reaching an unexpected state.

Defence

How is it prevented and fixed?

Implementation

Implementation-phase defence

Detail
Regularly wrap sub-expressions in parentheses, especially in security-critical code.

Verification

How is it detected?

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.)