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ID

CWE-643: Improper Neutralization of Data within XPath Expressions ('XPath Injection')

Weakness ID: 643
Abstraction: Base
Structure: Simple
Status: Incomplete
Presentation Filter:
+ Description
The software uses external input to dynamically construct an XPath expression used to retrieve data from an XML database, but it does not neutralize or incorrectly neutralizes that input. This allows an attacker to control the structure of the query.
+ Extended Description
The net effect is that the attacker will have control over the information selected from the XML database and may use that ability to control application flow, modify logic, retrieve unauthorized data, or bypass important checks (e.g. authentication).
+ 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)
+ Relevant to the view "Architectural Concepts" (CWE-1008)
NatureTypeIDName
MemberOfCategoryCategory1019Validate Inputs
+ Relevant to the view "Development Concepts" (CWE-699)
+ 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
ImplementationREALIZATION: This weakness is caused during implementation of an architectural security tactic.
+ 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

(Language-Independent classes): (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
Access Control

Technical Impact: Bypass Protection Mechanism

Controlling application flow (e.g. bypassing authentication).
Confidentiality

Technical Impact: Read Application Data

The attacker could read restricted XML content.
+ Likelihood Of Exploit
High
+ Demonstrative Examples

Example 1

Consider the following simple XML document that stores authentication information and a snippet of Java code that uses XPath query to retrieve authentication information:

(informative)
Example Language: XML 
<users>
<user>
<login>john</login>
<password>abracadabra</password>
<home_dir>/home/john</home_dir>

</user>
<user>
<login>cbc</login>
<password>1mgr8</password>
<home_dir>/home/cbc</home_dir>

</user>

</users>

The Java code used to retrieve the home directory based on the provided credentials is:

(bad)
Example Language: Java 
XPath xpath = XPathFactory.newInstance().newXPath();
XPathExpression xlogin = xpath.compile("//users/user[login/text()='" + login.getUserName() + "' and password/text() = '" + login.getPassword() + "']/home_dir/text()");
Document d = DocumentBuilderFactory.newInstance().newDocumentBuilder().parse(new File("db.xml"));
String homedir = xlogin.evaluate(d);

Assume that user "john" wishes to leverage XPath Injection and login without a valid password. By providing a username "john" and password "' or ''='" the XPath expression now becomes

(attack)
 
//users/user[login/text()='john' or ''='' and password/text() = '' or ''='']/home_dir/text()

which, of course, lets user "john" login without a valid password, thus bypassing authentication.

+ Potential Mitigations

Phase: Implementation

Use parameterized XPath queries (e.g. using XQuery). This will help ensure separation between data plane and control plane.

Phase: Implementation

Properly validate user input. Reject data where appropriate, filter where appropriate and escape where appropriate. Make sure input that will be used in XPath queries is safe in that context.
+ 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
MemberOfCategoryCategory990SFP Secondary Cluster: Tainted Input to Command
+ Notes

Relationship

This weakness is similar to other weaknesses that enable injection style attacks, such as SQL injection, command injection and LDAP injection. The main difference is that the target of attack here is the XML database.
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
WASC39XPath Injection
Software Fault PatternsSFP24Tainted input to command
+ References
[REF-531] Web Application Security Consortium. "XPath Injection". <http://www.webappsec.org/projects/threat/classes/xpath_injection.shtml>.
[REF-62] Mark Dowd, John McDonald and Justin Schuh. "The Art of Software Security Assessment". Chapter 17, "XPath Injection", Page 1070.. 1st Edition. Addison Wesley. 2006.
+ Content History
Submissions
Submission DateSubmitterOrganizationSource
2008-01-30Evgeny LebanidzeCigital
Modifications
Modification DateModifierOrganizationSource
2008-09-08CWE Content TeamMITRE
updated Common_Consequences, Relationships
2008-10-14CWE Content TeamMITRE
updated Description, Name, References, Relationship_Notes
2009-03-10CWE Content TeamMITRE
updated Demonstrative_Examples
2009-05-27CWE Content TeamMITRE
updated Name
2009-10-29CWE Content TeamMITRE
updated Common_Consequences
2010-02-16CWE Content TeamMITRE
updated Taxonomy_Mappings
2010-04-05CWE Content TeamMITRE
updated Description, Name
2010-06-21CWE Content TeamMITRE
updated Enabling_Factors_for_Exploitation
2010-12-13CWE Content TeamMITRE
updated Common_Consequences
2011-06-01CWE Content TeamMITRE
updated Common_Consequences
2012-05-11CWE Content TeamMITRE
updated References, Relationships
2012-10-30CWE Content TeamMITRE
updated Potential_Mitigations
2014-06-23CWE Content TeamMITRE
updated Relationships
2014-07-30CWE Content TeamMITRE
updated Relationships, Taxonomy_Mappings
2017-11-08CWE Content TeamMITRE
updated Applicable_Platforms, Enabling_Factors_for_Exploitation, Modes_of_Introduction, Relationships
Previous Entry Names
Change DatePrevious Entry Name
2008-10-14Unsafe Treatment of XPath Input
2009-05-27Failure to Sanitize Data within XPath Expressions (aka 'XPath injection')
2010-04-05Failure to Sanitize Data within XPath Expressions ('XPath injection')

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Page Last Updated: November 14, 2017