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.)
CWE-643 Base Incomplete
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.
Auswirkungen in der Praxis
Real-world CVEs caused by CWE-643
Bisher sind in MITREs Katalog keine öffentlichen CVE-Referenzen mit dieser CWE verknüpft.
Wie Angreifer es ausnutzen
Angreiferpfad Schritt für Schritt
- 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
The Java code used to retrieve the home directory based on the provided credentials is:
- 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
This lets user "john" login without a valid password, thus bypassing authentication.
Verwundbares Codebeispiel
Vulnerable Java
The Java code used to retrieve the home directory based on the provided credentials is:
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); Angreifer-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
//users/user[login/text()='john' or ''='' and password/text() = '' or ''='']/home_dir/text() Sicheres Codebeispiel
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.
Präventions-Checkliste
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.
Erkennungssignale
How to detect CWE-643
CWE-643
Don't catalog this weakness. Prove it's reachable.
Plexicus turns CWE catalogs into evidence: every CWE-pattern is matched against your real code graph, reach is proven on a sandbox clone, and verified findings ship as reviewed PRs.
Häufig gestellte Fragen Was ist CWE-643?
Wie gravierend ist CWE-643?
Welche Sprachen oder Plattformen sind von CWE-643 betroffen?
Wie kann ich CWE-643 verhindern?
Wie erkennt und behebt Plexicus CWE-643?
Wo erfahre ich mehr über CWE-643?
Frequently asked questions
Was ist 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.
Wie gravierend ist CWE-643?
MITRE stuft die Exploit-Wahrscheinlichkeit als hoch ein — diese Schwachstelle wird aktiv in freier Wildbahn ausgenutzt und sollte priorisiert behoben werden.
Welche Sprachen oder Plattformen sind von CWE-643 betroffen?
MITRE hat für diese CWE keine betroffenen Plattformen spezifiziert — sie kann in den meisten Anwendungs-Stacks auftreten.
Wie kann ich CWE-643 verhindern?
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.
Wie erkennt und behebt Plexicus CWE-643?
Die SAST-Engine von Plexicus erkennt die Datenfluss-Signatur von CWE-643 bei jedem Commit. Bei einem Treffer öffnet unser Codex-Remedium-Agent einen Fix-PR mit korrigiertem Code, Tests und einer einzeiligen Zusammenfassung für den Reviewer.
Wo erfahre ich mehr über CWE-643?
MITRE veröffentlicht die kanonische Definition unter https://cwe.mitre.org/data/definitions/643.html. Für ergänzende Hinweise kannst du auch die OWASP- und NIST-Dokumentation heranziehen.
Verwandte Schwachstellen
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…
Bereit, das Wesentliche zu validieren?
Bereit zu validieren, was zählt.
Plexicus ist Proof-Driven AppSec: validierte Funde, kontextuelles Verständnis und geprüfte Remediation — in Evidenz verankert, mit Ihnen gescoped.