CWE

Improper Handling of Inconsistent Special Elements

ID: 168		Date: (C)2012-05-14   (M)2022-10-10
Type: weakness		Status: DRAFT
Abstraction Type: Base

Description

The software does not handle when an inconsistency exists between two or more special characters or reserved words.

Extended Description

An example of this problem would be if paired characters appear in the wrong order, or if the special characters are not properly nested.

Applicable Platforms
Language Class: All

Time Of Introduction

• Implementation

Common Consequences

Scope	Technical Impact	Notes
Availability Access_Control Non-Repudiation	DoS: crash / exit / restart Bypass protection mechanism Hide activities

Detection Methods
None

Potential Mitigations

Phase	Strategy	Description	Effectiveness	Notes
		Developers should anticipate that inconsistent special elements will be injected/manipulated in the input vectors of their software system. Use an appropriate combination of black lists and white lists to ensure only valid, expected and appropriate input is processed by the system.
Implementation	Input Validation	Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a whitelist of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does. When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue." Do not rely exclusively on looking for malicious or malformed inputs (i.e., do not rely on a blacklist). A blacklist is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, blacklists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
Implementation	Input Validation	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 whitelist validation schemes by introducing dangerous inputs after they have been checked.

Relationships

Related CWE	Type	View	Chain
CWE-168 ChildOf CWE-896	Category	CWE-888

Demonstrative Examples
None

White Box Definitions
None

Black Box Definitions
None

Taxynomy Mappings

Taxynomy	Id	Name	Fit
PLOVER		Inconsistent Special Elements

References:
None