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.

Primary

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.

XXE
An acronym used for the term "XML eXternal Entities"

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

Confidentiality
Read Application Data
Read Files or Directories
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.

Integrity
Bypass Protection Mechanism
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.

Availability
DoS: Resource Consumption (CPU)
DoS: Resource Consumption (Memory)
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.

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.)
High

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

CVE-2022-42745
Recruiter software allows reading arbitrary files using XXE
https://www.cve.org/CVERecord?id=CVE-2022-42745

CVE-2005-1306
A browser control can allow remote attackers to determine the existence of files via Javascript containing XML script.
https://www.cve.org/CVERecord?id=CVE-2005-1306

CVE-2012-5656
XXE during SVG image conversion
https://www.cve.org/CVERecord?id=CVE-2012-5656

CVE-2012-2239
XXE in PHP application allows reading the application's configuration file.
https://www.cve.org/CVERecord?id=CVE-2012-2239

CVE-2012-3489
XXE in database server
https://www.cve.org/CVERecord?id=CVE-2012-3489

CVE-2012-4399
XXE in rapid web application development framework allows reading arbitrary files.
https://www.cve.org/CVERecord?id=CVE-2012-4399

CVE-2012-3363
XXE via XML-RPC request.
https://www.cve.org/CVERecord?id=CVE-2012-3363

CVE-2012-0037
XXE in office document product using RDF.
https://www.cve.org/CVERecord?id=CVE-2012-0037

CVE-2011-4107
XXE in web-based administration tool for database.
https://www.cve.org/CVERecord?id=CVE-2011-4107

CVE-2010-3322
XXE in product that performs large-scale data analysis.
https://www.cve.org/CVERecord?id=CVE-2010-3322

CVE-2009-1699
XXE in XSL stylesheet functionality in a common library used by some web browsers.
https://www.cve.org/CVERecord?id=CVE-2009-1699

43
XML External Entities

SFP24
Tainted input to command

Allowed
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.
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.

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.

Anonymous Tool Vendor (under NDA)
2007-05-07
Draft 6
2007-05-07

Eric Dalci
Cigital
2008-07-01
updated Time_of_Introduction

CWE Content Team
MITRE
2008-09-08
updated Description, Relationships, Observed_Example, Other_Notes, Taxonomy_Mappings

CWE Content Team
MITRE
2010-02-16
updated Taxonomy_Mappings

CWE Content Team
MITRE
2010-09-27
updated Background_Details, Other_Notes

CWE Content Team
MITRE
2011-03-29
updated Name

CWE Content Team
MITRE
2011-06-01
updated Common_Consequences

CWE Content Team
MITRE
2012-05-11
updated Relationships

CWE Content Team
MITRE
2013-02-21
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
updated Relationships, Taxonomy_Mappings

CWE Content Team
MITRE
2015-12-07
updated Relationships

CWE Content Team
MITRE
2017-11-08
updated Modes_of_Introduction, References, Relationships, Relevant_Properties

CWE Content Team
MITRE
2018-03-27
updated Relationships

CWE Content Team
MITRE
2019-01-03
updated Related_Attack_Patterns

CWE Content Team
MITRE
2019-06-20
updated Name, Type

CWE Content Team
MITRE
2019-09-19
updated Relationships

CWE Content Team
MITRE
2020-02-24
updated Applicable_Platforms, Relationships

CWE Content Team
MITRE
2020-08-20
updated Relationships

CWE Content Team
MITRE
2020-12-10
updated Relationships

CWE Content Team
MITRE
2021-07-20
updated Relationships

CWE Content Team
MITRE
2021-10-28
updated Relationships

CWE Content Team
MITRE
2022-06-28
updated Relationships

CWE Content Team
MITRE
2023-01-31
updated Alternate_Terms, Common_Consequences, Description

CWE Content Team
MITRE
2023-04-27
updated Detection_Factors, References, Relationships

CWE Content Team
MITRE
2023-06-29
updated Mapping_Notes

CWE Content Team
MITRE
2023-10-26
updated Observed_Examples

CWE Content Team
MITRE
2025-09-09
4.18
2025-09-09
updated References

CWE Content Team
MITRE
2025-12-11
4.19
2025-12-11
updated Applicable_Platforms, Background_Details, Common_Consequences, Description, Diagram, Relationships, Weakness_Ordinalities

Information Leak Through XML External Entity File Disclosure
Information Exposure Through XML External Entity Reference
Improper Restriction of XML External Entity Reference ('XXE')