CWE

Common Weakness Enumeration

A Community-Developed List of Software Weakness Types

CWE/SANS Top 25 Most Dangerous Software Errors
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ID

CWE-454: External Initialization of Trusted Variables or Data Stores

Weakness ID: 454
Abstraction: Base
Structure: Simple
Status: Draft
Presentation Filter:
+ Description
The software initializes critical internal variables or data stores using inputs that can be modified by untrusted actors.
+ Extended Description
A software system should be reluctant to trust variables that have been initialized outside of its trust boundary, especially if they are initialized by users. The variables may have been initialized incorrectly. If an attacker can initialize the variable, then they can influence what the vulnerable system will do.
+ Relationships

The table(s) below shows the weaknesses and high level categories that are related to this weakness. These relationships are defined as ChildOf, ParentOf, MemberOf and give insight to similar items that may exist at higher and lower levels of abstraction. In addition, relationships such as PeerOf and CanAlsoBe are defined to show similar weaknesses that the user may want to explore.

+ Relevant to the view "Research Concepts" (CWE-1000)
NatureTypeIDName
ChildOfClassClass665Improper Initialization
CanAlsoBeBaseBase456Missing Initialization of a Variable
+ Relevant to the view "Development Concepts" (CWE-699)
NatureTypeIDName
MemberOfCategoryCategory452Initialization and Cleanup Errors
+ Modes Of Introduction

The different Modes of Introduction provide information about how and when this weakness may be introduced. The Phase identifies a point in the software life cycle at which introduction may occur, while the Note provides a typical scenario related to introduction during the given phase.

PhaseNote
Architecture and Design
Implementation
+ Applicable Platforms
The listings below show possible areas for which the given weakness could appear. These may be for specific named Languages, Operating Systems, Architectures, Paradigms, Technologies, or a class of such platforms. The platform is listed along with how frequently the given weakness appears for that instance.

Languages

PHP (Sometimes Prevalent)

Class: Language-Independent (Undetermined Prevalence)

+ Common Consequences

The table below specifies different individual consequences associated with the weakness. The Scope identifies the application security area that is violated, while the Impact describes the negative technical impact that arises if an adversary succeeds in exploiting this weakness. The Likelihood provides information about how likely the specific consequence is expected to be seen relative to the other consequences in the list. For example, there may be high likelihood that a weakness will be exploited to achieve a certain impact, but a low likelihood that it will be exploited to achieve a different impact.

ScopeImpactLikelihood
Integrity

Technical Impact: Modify Application Data

An attacker could gain access to and modify sensitive data or system information.
+ Demonstrative Examples

Example 1

In the Java example below, a system property controls the debug level of the application.

(bad code)
Example Language: Java 
int debugLevel = Integer.getInteger("com.domain.application.debugLevel").intValue();

If an attacker is able to modify the system property, then it may be possible to coax the application into divulging sensitive information by virtue of the fact that additional debug information is printed/exposed as the debug level increases.

Example 2

This code checks the HTTP POST request for a debug switch, and enables a debug mode if the switch is set.

(bad code)
Example Language: PHP 
$debugEnabled = false;
if ($_POST["debug"] == "true"){
$debugEnabled = true;

}
/.../

function login($username, $password){
if($debugEnabled){
echo 'Debug Activated';
phpinfo();
$isAdmin = True;
return True;

}

}

Any user can activate the debug mode, gaining administrator privileges. An attacker may also use the information printed by the phpinfo() function to further exploit the system. .

This example also exhibits Information Exposure Through Debug Information (CWE-215)

+ Observed Examples
ReferenceDescription
Does not clear dangerous environment variables, enabling symlink attack.
Specify alternate configuration directory in environment variable, enabling untrusted path.
Dangerous environment variable not cleansed.
Specify arbitrary modules using environment variable.
+ Potential Mitigations

Phase: Implementation

Strategy: Input Validation

A software system should be reluctant to trust variables that have been initialized outside of its trust boundary. Ensure adequate checking (e.g. input validation) is performed when relying on input from outside a trust boundary.

Phase: Architecture and Design

Avoid any external control of variables. If necessary, restrict the variables that can be modified using a whitelist, and use a different namespace or naming convention if possible.
+ Memberships
This MemberOf Relationships table shows additional CWE Categories and Views that reference this weakness as a member. This information is often useful in understanding where a weakness fits within the context of external information sources.
NatureTypeIDName
MemberOfCategoryCategory8082010 Top 25 - Weaknesses On the Cusp
MemberOfViewView884CWE Cross-section
MemberOfCategoryCategory994SFP Secondary Cluster: Tainted Input to Variable
+ Notes

Applicable Platform

This is often found in PHP due to register_globals and the common practice of storing library/include files under the web document root so that they are available using a direct request.

Relationship

Overlaps Missing variable initialization, especially in PHP.
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
PLOVERExternal initialization of trusted variables or values
Software Fault PatternsSFP25Tainted input to variable
+ Content History
Submissions
Submission DateSubmitterOrganization
PLOVER
Modifications
Modification DateModifierOrganization
2008-07-01Sean EidemillerCigital
added/updated demonstrative examples
2008-07-01Eric DalciCigital
updated Potential_Mitigations, Time_of_Introduction
2008-09-08CWE Content TeamMITRE
updated Applicable_Platforms, Description, Relationships, Other_Notes, Taxonomy_Mappings
2009-10-29CWE Content TeamMITRE
updated Other_Notes, Relationship_Notes
2010-02-16CWE Content TeamMITRE
updated Description, Name, Relationships
2010-04-05CWE Content TeamMITRE
updated Applicable_Platforms, Demonstrative_Examples
2011-03-29CWE Content TeamMITRE
updated Demonstrative_Examples
2011-06-01CWE Content TeamMITRE
updated Common_Consequences, Relationships, Taxonomy_Mappings
2012-05-11CWE Content TeamMITRE
updated Common_Consequences, Relationships, Taxonomy_Mappings
2012-10-30CWE Content TeamMITRE
updated Potential_Mitigations
2014-07-30CWE Content TeamMITRE
updated Relationships, Taxonomy_Mappings
2017-11-08CWE Content TeamMITRE
updated Description
Previous Entry Names
Change DatePrevious Entry Name
2008-04-11External Initialization of Trusted Variables or Values
2010-02-16External Initialization of Trusted Variables

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Page Last Updated: January 18, 2018