Incorrect Behavior Order: Early Validation
Weakness ID: 179 (Weakness Base)Status: Incomplete
+ Description

Description Summary

The software validates input before applying protection mechanisms that modify the input, which could allow an attacker to bypass the validation via dangerous inputs that only arise after the modification.

Extended Description

Software needs to validate data at the proper time, after data has been canonicalized and cleansed. Early validation is susceptible to various manipulations that result in dangerous inputs that are produced by canonicalization and cleansing.

+ Time of Introduction
  • Implementation
+ Applicable Platforms



+ Modes of Introduction

Since early validation errors usually arise from improperly implemented defensive mechanisms, it is likely that these will be introduced more frequently as secure programming becomes implemented more widely.

+ Potential Mitigations

Inputs should be decoded and canonicalized to the application's current internal representation before being validated. Make sure that your application does not decode the same input twice. Such errors could be used to bypass whitelist schemes by introducing dangerous inputs after they have been checked.

+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfCategoryCategory171Cleansing, Canonicalization, and Comparison Errors
Development Concepts (primary)699
ChildOfWeakness ClassWeakness Class693Protection Mechanism Failure
Research Concepts1000
ChildOfWeakness ClassWeakness Class696Incorrect Behavior Order
Research Concepts (primary)1000
ChildOfCategoryCategory722OWASP Top Ten 2004 Category A1 - Unvalidated Input
Weaknesses in OWASP Top Ten (2004) (primary)711
ParentOfWeakness BaseWeakness Base180Incorrect Behavior Order: Validate Before Canonicalize
Research Concepts (primary)1000
ParentOfWeakness BaseWeakness Base181Incorrect Behavior Order: Validate Before Filter
Research Concepts (primary)1000
+ Research Gaps

These errors are mostly reported in path traversal vulnerabilities, but the concept applies anyplace where filtering occurs.

+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
PLOVEREarly Validation Errors
+ Related Attack Patterns
CAPEC-IDAttack Pattern Name
(CAPEC Version: 1.4)
3Using Leading 'Ghost' Character Sequences to Bypass Input Filters
43Exploiting Multiple Input Interpretation Layers
71Using Unicode Encoding to Bypass Validation Logic
+ Content History
Submission DateSubmitterOrganizationSource
PLOVERExternally Mined
Modification DateModifierOrganizationSource
2008-07-01Eric DalciCigitalExternal
updated Potential Mitigations, Time of Introduction
Suggested OWASP Top Ten 2004 mapping
2008-09-08CWE Content TeamMITREInternal
updated Modes of Introduction, Relationships, Taxonomy Mappings
2008-10-14CWE Content TeamMITREInternal
updated Description
2009-03-10CWE Content TeamMITREInternal
updated Relationships
Previous Entry Names
Change DatePrevious Entry Name
2008-04-11Early Validation Errors