CAPEC-83 XPath Injection

CAPEC ID: 83

CAPEC-83 Metadata

Likelihood of Attack

High

Typical Severity

High

Overview

Summary

An attacker can craft special user-controllable input consisting of XPath expressions to inject the XML database and bypass authentication or glean information that they normally would not be able to. XPath Injection enables an attacker to talk directly to the XML database, thus bypassing the application completely. XPath Injection results from the failure of an application to properly sanitize input used as part of dynamic XPath expressions used to query an XML database.

Prerequisites

XPath queries used to retrieve information stored in XML documents User-controllable input not properly sanitized before being used as part of XPath queries

Execution Flow

Step Phase Description Techniques
1 Explore [Survey the target] Using a browser or an automated tool, an adversary records all instances of user-controllable input used to contruct XPath queries.
  • Use an automated tool to record all instances of user-controllable input used to contruct XPath queries.
  • Use a browser to manually explore the website and analyze how the application processes inputs.
2 Explore [Determine the tructure of queries] Using manual or automated means, test inputs found for XPath weaknesses.
  • Use an automated tool automatically probe the inputs for XPath weaknesses.
  • Manually probe the inputs using characters such as single quote (') that can cause XPath-releated errors, thus indicating an XPath weakness.
3 Exploit [Inject content into XPath query] Craft malicious content containing XPath expressions that is not validated by the application and is executed as part of the XPath queries.
  • Use the crafted input to execute unexpected queries that can disclose sensitive database information to the attacker.
  • Use a combination of single quote (') and boolean expressions such as "or 1=1" to manipulate XPath logic.
  • Use XPath functions in the malicious content such as "string-length", "substring", or "count" to gain information about the XML document structure being used.

Potential Solutions / Mitigations

Strong input validation - All user-controllable input must be validated and filtered for illegal characters as well as content that can be interpreted in the context of an XPath expression. Characters such as a single-quote(') or operators such as or (|), and (&) and such should be filtered if the application does not expect them in the context in which they appear. If such content cannot be filtered, it must at least be properly escaped to avoid them being interpreted as part of XPath expressions. Use of parameterized XPath queries - Parameterization causes the input to be restricted to certain domains, such as strings or integers, and any input outside such domains is considered invalid and the query fails. Use of custom error pages - Attackers can glean information about the nature of queries from descriptive error messages. Input validation must be coupled with customized error pages that inform about an error without disclosing information about the database or application.

Related Weaknesses (CWE)

CWE ID Description
CWE-20 Improper Input Validation
CWE-74 Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')
CWE-91 XML Injection (aka Blind XPath Injection)
CWE-707 Improper Neutralization

Related CAPECs

CAPEC ID Description
CAPEC-250 An attacker utilizes crafted XML user-controllable input to probe, attack, and inject data into the XML database, using techniques similar to SQL injection. The user-controllable input can allow for unauthorized viewing of data, bypassing authentication or the front-end application for direct XML database access, and possibly altering database information.

Taxonomy Mappings

Taxonomy: WASC

Entry ID Entry Name
39 XPath Injection

Taxonomy: OWASP Attacks

Entry ID Entry Name
Link XPATH Injection

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