CWE-643 Base Incomplete High likelihood

Improper Neutralization of Data within XPath Expressions ('XPath Injection')

XPath Injection occurs when an application uses unvalidated user input to build an XPath query for an XML database. Without proper sanitization, attackers can manipulate the query's structure.

Definition

What is CWE-643?

XPath Injection occurs when an application uses unvalidated user input to build an XPath query for an XML database. Without proper sanitization, attackers can manipulate the query's structure.
This vulnerability allows an attacker to alter the intended logic of the XPath expression. By injecting special characters or control sequences, they can change which data is retrieved from the XML source, potentially bypassing application logic, authentication, or access controls. Successful exploitation can lead to unauthorized data exposure, information disclosure, or manipulation of application flow. Developers must treat all user input used in XPath queries as untrusted and implement proper validation or parameterization to prevent these attacks.
Real-world impact

Real-world CVEs caused by CWE-643

No public CVE references are linked to this CWE in MITRE's catalog yet.

How attackers exploit it

Step-by-step attacker path

  1. 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:

  2. 2

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

  3. 3

    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

  4. 4

    This lets user "john" login without a valid password, thus bypassing authentication.

Vulnerable code example

Vulnerable Java

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

Vulnerable 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);
Attacker payload

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

Attacker payload 
//users/user[login/text()='john' or ''='' and password/text() = '' or ''='']/home_dir/text()
Secure code example

Secure pseudo

Secure pseudo 
// Validate, sanitize, or use a safe API before reaching the sink.
function handleRequest(input) {
  const safe = validateAndEscape(input);
  return executeWithGuards(safe);
}
What changed: the unsafe sink is replaced (or the input is validated/escaped) so the same payload no longer triggers the weakness.
Prevention checklist

How to prevent CWE-643

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

How to detect CWE-643

Automated Static Analysis High

Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc.)

Plexicus auto-fix

Plexicus auto-detects CWE-643 and opens a fix PR in under 60 seconds.

Codex Remedium scans every commit, identifies this exact weakness, and ships a reviewer-ready pull request with the patch. No tickets. No hand-offs.

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Frequently asked questions

Frequently asked questions

What is CWE-643?

XPath Injection occurs when an application uses unvalidated user input to build an XPath query for an XML database. Without proper sanitization, attackers can manipulate the query's structure.

How serious is CWE-643?

MITRE rates the likelihood of exploit as High — this weakness is actively exploited in the wild and should be prioritized for remediation.

What languages or platforms are affected by CWE-643?

MITRE has not specified affected platforms for this CWE — it can apply across most application stacks.

How can I prevent CWE-643?

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

How does Plexicus detect and fix CWE-643?

Plexicus's SAST engine matches the data-flow signature for CWE-643 on every commit. When a match is found, our Codex Remedium agent opens a fix PR with the corrected code, tests, and a one-line summary for the reviewer.

Where can I learn more about CWE-643?

MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/643.html. You can also reference OWASP and NIST documentation for adjacent guidance.

Related weaknesses

Weaknesses related to CWE-643

CWE-943 Parent

Improper Neutralization of Special Elements in Data Query Logic

This vulnerability occurs when an application builds a query for a data store (like a database) but fails to properly sanitize…

CWE-652 Sibling

Improper Neutralization of Data within XQuery Expressions ('XQuery Injection')

XQuery Injection occurs when an application uses unvalidated user input to build an XQuery expression for querying an XML database.…

CWE-89 Sibling

Improper Neutralization of Special Elements used in an SQL Command ('SQL Injection')

SQL Injection occurs when an application builds a database query using untrusted user input without properly sanitizing it. This allows an…

CWE-90 Sibling

Improper Neutralization of Special Elements used in an LDAP Query ('LDAP Injection')

This vulnerability occurs when an application builds an LDAP query using untrusted user input without properly sanitizing it. An attacker…

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