CWE

Common Weakness Enumeration

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CWE-212: Improper Cross-boundary Removal of Sensitive Data

 
Improper Cross-boundary Removal of Sensitive Data
Weakness ID: 212 (Weakness Base)Status: Incomplete
+ Description

Description Summary

The software uses a resource that contains sensitive data, but it does not properly remove that data before it stores, transfers, or shares the resource with actors in another control sphere.

Extended Description

Resources that may contain sensitive data include documents, packets, messages, databases, etc. While this data may be useful to an individual user or small set of users who share the resource, it may need to be removed before the resource can be shared outside of the trusted group. The process of removal is sometimes called cleansing or scrubbing.

For example, software that is used for editing documents might not remove sensitive data such as reviewer comments or the local pathname where the document is stored. Or, a proxy might not remove an internal IP address from headers before making an outgoing request to an Internet site.

+ Terminology Notes

The terms "cleansing" and "scrubbing" have multiple uses within computing. In information security, these are used for the removal of sensitive data, but they are also used for the modification of incoming/outgoing data so that it conforms to specifications.

+ Time of Introduction
  • Architecture and Design
  • Implementation
  • Operation
+ Applicable Platforms

Languages

Language-independent

+ Common Consequences
ScopeEffect

Technical Impact: Read files or directories; Read application data

Sensitive data may be exposed to an unauthorized actor in another control sphere. This may have a wide range of secondary consequences which will depend on what data is exposed. One possibility is the exposure of system data allowing an attacker to craft a specific, more effective attack.

+ Demonstrative Examples

Example 1

This code either generates a public HTML user information page or a JSON response containing the same user information.

(Bad Code)
Example Language: PHP 
// API flag, output JSON if set
$json = $_GET['json']
$username = $_GET['user']
if(!$json)
{
$record = getUserRecord($username);
foreach($record as $fieldName => $fieldValue)
{
if($fieldName == "email_address") {
// skip displaying user emails
continue;
}
else{
writeToHtmlPage($fieldName,$fieldValue);
}
}
}
else
{
$record = getUserRecord($username);
echo json_encode($record);
}

The programmer is careful to not display the user's e-mail address when displaying the public HTML page. However, the e-mail address is not removed from the JSON response, exposing the user's e-mail address.

+ Observed Examples
ReferenceDescription
Some image editors modify a JPEG image, but the original EXIF thumbnail image is left intact within the JPEG. (Also an interaction error).
NAT feature in firewall leaks internal IP addresses in ICMP error messages.
+ Potential Mitigations

Phase: Requirements

Clearly specify which information should be regarded as private or sensitive, and require that the product offers functionality that allows the user to cleanse the sensitive information from the resource before it is published or exported to other parties.

Phase: Architecture and Design

Strategy: Separation of Privilege

Compartmentalize the system to have "safe" areas where trust boundaries can be unambiguously drawn. Do not allow sensitive data to go outside of the trust boundary and always be careful when interfacing with a compartment outside of the safe area.

Ensure that appropriate compartmentalization is built into the system design and that the compartmentalization serves to allow for and further reinforce privilege separation functionality. Architects and designers should rely on the principle of least privilege to decide when it is appropriate to use and to drop system privileges.

Phase: Implementation

Strategy: Identify and Reduce Attack Surface

Use naming conventions and strong types to make it easier to spot when sensitive data is being used. When creating structures, objects, or other complex entities, separate the sensitive and non-sensitive data as much as possible.

Effectiveness: Defense in Depth

This makes it easier to spot places in the code where data is being used that is unencrypted.

Phase: Implementation

Avoid errors related to improper resource shutdown or release (CWE-404), which may leave the sensitive data within the resource if it is in an incomplete state.

+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfWeakness ClassWeakness Class200Information Exposure
Development Concepts (primary)699
Research Concepts (primary)1000
ChildOfWeakness ClassWeakness Class669Incorrect Resource Transfer Between Spheres
Research Concepts1000
ChildOfCategoryCategory8082010 Top 25 - Weaknesses On the Cusp
Weaknesses in the 2010 CWE/SANS Top 25 Most Dangerous Programming Errors (primary)800
ChildOfCategoryCategory8672011 Top 25 - Weaknesses On the Cusp
Weaknesses in the 2011 CWE/SANS Top 25 Most Dangerous Software Errors (primary)900
ChildOfCategoryCategory895SFP Cluster: Information Leak
Software Fault Pattern (SFP) Clusters (primary)888
MemberOfViewView884CWE Cross-section
CWE Cross-section (primary)884
CanAlsoBeWeakness BaseWeakness Base226Sensitive Information Uncleared Before Release
Research Concepts1000
+ Relationship Notes

This entry is intended to be different from resultant information leaks, including those that occur from improper buffer initialization and reuse, improper encryption, interaction errors, and multiple interpretation errors. This entry could be regarded as a privacy leak, depending on the type of information that is leaked.

There is a close association between CWE-226 and CWE-212. The difference is partially that of perspective. CWE-226 is geared towards the final stage of the resource lifecycle, in which the resource is deleted, eliminated, expired, or otherwise released for reuse. Technically, this involves a transfer to a different control sphere, in which the original contents of the resource are no longer relevant. CWE-212, however, is intended for sensitive data in resources that are intentionally shared with others, so they are still active. This distinction is useful from the perspective of the CWE research view (CWE-1000).

+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
PLOVERCross-Boundary Cleansing Infoleak
+ Content History
Submissions
Submission DateSubmitterOrganizationSource
Externally Mined
Modifications
Modification DateModifierOrganizationSource
2008-07-01CigitalExternal
updated Time_of_Introduction
2008-09-08MITREInternal
updated Relationships, Other_Notes, Taxonomy_Mappings
2008-10-14MITREInternal
updated Description
2009-10-29MITREInternal
updated Description, Other_Notes, Relationship_Notes
2009-12-28MITREInternal
updated Name
2010-02-16MITREInternal
updated Applicable_Platforms, Common_Consequences, Description, Name, Observed_Examples, Potential_Mitigations, Relationship_Notes, Relationships, Terminology_Notes
2010-04-05MITREInternal
updated Related_Attack_Patterns
2010-06-21MITREInternal
updated Potential_Mitigations
2010-09-27MITREInternal
updated Potential_Mitigations
2011-06-01MITREInternal
updated Common_Consequences
2011-06-27MITREInternal
updated Demonstrative_Examples, Relationships
2012-05-11MITREInternal
updated Relationships
2012-10-30MITREInternal
updated Potential_Mitigations
Previous Entry Names
Change DatePrevious Entry Name
2009-12-28Cross-boundary Cleansing Information Leak
2010-02-16Improper Cross-boundary Cleansing
Page Last Updated: June 23, 2014