COMMON WEAKNESS ENUMERATIONDraft

CWE-180

Incorrect Behavior Order: Validate Before Canonicalize

The product validates input before it is canonicalized, which prevents the product from detecting data that becomes invalid after the canonicalization step.

Abstraction

Variant

Structure

Simple

Likelihood of Exploit

Medium

Understand the problem

What is the problem?

The product validates input before it is canonicalized, which prevents the product from detecting data that becomes invalid after the canonicalization step.

Extended description

This can be used by an attacker to bypass the validation and launch attacks that expose weaknesses that would otherwise be prevented, such as injection.

Root cause

How and when does the problem arise?

Lifecycle phase

Implementation

Risk

What does successful exploitation lead to?

Bypass Protection Mechanism

Affected security scopes: Access Control

Defence

How is it prevented and fixed?

Implementation

Input Validation

Detail
Inputs should be decoded and canonicalized to the application's current internal representation before being validated (CWE-180). Make sure that the application does not decode the same input twice (CWE-174). Such errors could be used to bypass allowlist validation schemes by introducing dangerous inputs after they have been checked.