CWE-611 Detail

CWE-611

Improper Restriction of XML External Entity Reference
Draft
2007-05-07
00h00 +00:00
2025-12-11
00h00 +00:00
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Name: Improper Restriction of XML External Entity Reference

The product processes an XML document that can contain XML entities with URIs that resolve to documents outside of the intended sphere of control, causing the product to embed incorrect documents into its output.

General Informations

Background Details

XML documents optionally contain a Document Type Definition (DTD), which, among other features, enables the definition of XML entities. It is possible to define an entity by providing a substitution string in the form of a URI. The XML parser can access the contents of this URI and embed these contents back into the XML document for further processing.

Modes Of Introduction

Implementation : REALIZATION: This weakness is caused during implementation of an architectural security tactic.

Applicable Platforms

Language

Class: Not Language-Specific (Undetermined)
Name: XML (Undetermined)

Technologies

Class: Not Technology-Specific (Undetermined)
Class: Web Based (Undetermined)

Common Consequences

Scope Impact Likelihood
ConfidentialityRead Application Data, Read Files or Directories

Note: If the attacker is able to include a crafted DTD and a default entity resolver is enabled, the attacker may be able to access arbitrary files on the system. By submitting an XML file that defines an external entity with a file:// URI, an attacker can cause the processing application to read the contents of a local file. For example, a URI such as "file:///c:/winnt/win.ini" designates (in Windows) the file C:\Winnt\win.ini, or file:///etc/passwd designates the password file in Unix-based systems. Once the content of the URI is read, it is fed back into the application that is processing the XML. This application may echo back the data (e.g., in an error message), thereby exposing the file contents.
IntegrityBypass Protection Mechanism

Note: An attacker may supply a crafted DTD using URIs with schemes such as http://, forcing the application to make outgoing HTTP requests to servers that the attacker cannot reach directly, which can be used to bypass firewall restrictions; hide the source of attacks such as port scanning; or otherwise leverage the server's trust relationship with other entities.
AvailabilityDoS: Resource Consumption (CPU), DoS: Resource Consumption (Memory)

Note: The product could consume excessive CPU cycles or memory using a URI that points to a large file, or a device that always returns data such as /dev/random. Alternately, the URI could reference a file that contains many nested or recursive entity references to further slow down parsing.

Observed Examples

References Description

CVE-2022-42745

Recruiter software allows reading arbitrary files using XXE

CVE-2005-1306

A browser control can allow remote attackers to determine the existence of files via Javascript containing XML script.

CVE-2012-5656

XXE during SVG image conversion

CVE-2012-2239

XXE in PHP application allows reading the application's configuration file.

CVE-2012-3489

XXE in database server

CVE-2012-4399

XXE in rapid web application development framework allows reading arbitrary files.

CVE-2012-3363

XXE via XML-RPC request.

CVE-2012-0037

XXE in office document product using RDF.

CVE-2011-4107

XXE in web-based administration tool for database.

CVE-2010-3322

XXE in product that performs large-scale data analysis.

CVE-2009-1699

XXE in XSL stylesheet functionality in a common library used by some web browsers.

Potential Mitigations

Phases : Implementation // System Configuration
Many XML parsers and validators can be configured to disable external entity expansion.

Detection Methods

Automated Static Analysis

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.)
Effectiveness : High

Vulnerability Mapping Notes

Justification : This CWE entry is at the Base level of abstraction, which is a preferred level of abstraction for mapping to the root causes of vulnerabilities.
Comment : Carefully read both the name and description to ensure that this mapping is an appropriate fit. Do not try to 'force' a mapping to a lower-level Base/Variant simply to comply with this preferred level of abstraction.

Related Attack Patterns

CAPEC-ID Attack Pattern Name
CAPEC-221 Data Serialization External Entities Blowup
This attack takes advantage of the entity replacement property of certain data serialization languages (e.g., XML, YAML, etc.) where the value of the replacement is a URI. A well-crafted file could have the entity refer to a URI that consumes a large amount of resources to create a denial of service condition. This can cause the system to either freeze, crash, or execute arbitrary code depending on the URI.

NotesNotes

CWE-918 (SSRF) and CWE-611 (XXE) are closely related, because they both involve web-related technologies and can launch outbound requests to unexpected destinations. However, XXE can be performed client-side, or in other contexts in which the software is not acting directly as a server, so the "Server" portion of the SSRF acronym does not necessarily apply.

References

REF-496

XML External Entity (XXE) Processing
OWASP.
https://www.owasp.org/index.php/XML_External_Entity_(XXE)_Processing

REF-497

XML External Entity Attacks (XXE)
Sascha Herzog.
https://mohemiv.com/files/XML_Exteral_Entity_Attack.pdf

REF-498

XXE (Xml eXternal Entity) Attack
Gregory Steuck.
https://seclists.org/bugtraq/2002/Oct/420/

REF-499

XML External Entities (XXE) Attack
WASC.
http://projects.webappsec.org/w/page/13247003/XML%20External%20Entities

REF-500

XML Denial of Service Attacks and Defenses
Bryan Sullivan.
https://learn.microsoft.com/en-us/archive/msdn-magazine/2009/november/xml-denial-of-service-attacks-and-defenses

REF-501

Preventing XXE in PHP
Chris Cornutt.
https://websec.io/2012/08/27/Preventing-XXE-in-PHP.html

Submission

Name Organization Date Date release Version
Anonymous Tool Vendor (under NDA) 2007-05-07 +00:00 2007-05-07 +00:00 Draft 6

Modifications

Name Organization Date Comment
Eric Dalci Cigital 2008-07-01 +00:00 updated Time_of_Introduction
CWE Content Team MITRE 2008-09-08 +00:00 updated Description, Relationships, Observed_Example, Other_Notes, Taxonomy_Mappings
CWE Content Team MITRE 2010-02-16 +00:00 updated Taxonomy_Mappings
CWE Content Team MITRE 2010-09-27 +00:00 updated Background_Details, Other_Notes
CWE Content Team MITRE 2011-03-29 +00:00 updated Name
CWE Content Team MITRE 2011-06-01 +00:00 updated Common_Consequences
CWE Content Team MITRE 2012-05-11 +00:00 updated Relationships
CWE Content Team MITRE 2013-02-21 +00:00 updated Alternate_Terms, Applicable_Platforms, Background_Details, Common_Consequences, Description, Name, Observed_Examples, Potential_Mitigations, References, Relationship_Notes, Relationships, Taxonomy_Mappings
CWE Content Team MITRE 2014-07-30 +00:00 updated Relationships, Taxonomy_Mappings
CWE Content Team MITRE 2015-12-07 +00:00 updated Relationships
CWE Content Team MITRE 2017-11-08 +00:00 updated Modes_of_Introduction, References, Relationships, Relevant_Properties
CWE Content Team MITRE 2018-03-27 +00:00 updated Relationships
CWE Content Team MITRE 2019-01-03 +00:00 updated Related_Attack_Patterns
CWE Content Team MITRE 2019-06-20 +00:00 updated Name, Type
CWE Content Team MITRE 2019-09-19 +00:00 updated Relationships
CWE Content Team MITRE 2020-02-24 +00:00 updated Applicable_Platforms, Relationships
CWE Content Team MITRE 2020-08-20 +00:00 updated Relationships
CWE Content Team MITRE 2020-12-10 +00:00 updated Relationships
CWE Content Team MITRE 2021-07-20 +00:00 updated Relationships
CWE Content Team MITRE 2021-10-28 +00:00 updated Relationships
CWE Content Team MITRE 2022-06-28 +00:00 updated Relationships
CWE Content Team MITRE 2023-01-31 +00:00 updated Alternate_Terms, Common_Consequences, Description
CWE Content Team MITRE 2023-04-27 +00:00 updated Detection_Factors, References, Relationships
CWE Content Team MITRE 2023-06-29 +00:00 updated Mapping_Notes
CWE Content Team MITRE 2023-10-26 +00:00 updated Observed_Examples
CWE Content Team MITRE 2025-09-09 +00:00 updated References
CWE Content Team MITRE 2025-12-11 +00:00 updated Applicable_Platforms, Background_Details, Common_Consequences, Description, Diagram, Relationships, Weakness_Ordinalities
The information presented on CVE Find originates from several carefully selected reference sources. CVE data is provided by MITRE Corporation and the National Vulnerability Database (NVD). The Known Exploited Vulnerabilities (KEV) catalog is sourced from the Cybersecurity and Infrastructure Security Agency (CISA), while EPSS scores come from FIRST.org. Additionally, data regarding software weaknesses (CWE) and common attack patterns (CAPEC) is maintained by MITRE Corporation, and information on hardware and software configurations (CPE) is provided by the NVD.