CWE - CWE-611: Improper Restriction of XML External Entity Reference (4.20)
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    CWE-611: Improper Restriction of XML External Entity Reference

    Weakness ID: 611
    Vulnerability Mapping: ALLOWED This CWE ID may be used to map to real-world vulnerabilities
    Abstraction: Base Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.
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    + Description
    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. Diagram for CWE-611
    + Alternate Terms
    XXE
    An acronym used for the term "XML eXternal Entities"
    + Common Consequences
    Section HelpThis table specifies different individual consequences associated with the weakness. The Scope identifies the application security area that is violated, while the Impact describes the negative technical impact that arises if an adversary succeeds in exploiting this weakness. The Likelihood provides information about how likely the specific consequence is expected to be seen relative to the other consequences in the list. For example, there may be high likelihood that a weakness will be exploited to achieve a certain impact, but a low likelihood that it will be exploited to achieve a different impact.
    Impact Details

    Read Application Data; Read Files or Directories

    		Scope: Confidentiality

    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.

    Bypass Protection Mechanism

    		Scope: Integrity

    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.

    DoS: Resource Consumption (CPU); DoS: Resource Consumption (Memory)

    		Scope: Availability

    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.
    + Potential Mitigations
    Phase(s) Mitigation

    Implementation; System Configuration
    Many XML parsers and validators can be configured to disable external entity expansion.
    + Relationships
    Section Help This table shows the weaknesses and high level categories that are related to this weakness. These relationships are defined as ChildOf, ParentOf, MemberOf and give insight to similar items that may exist at higher and lower levels of abstraction. In addition, relationships such as PeerOf and CanAlsoBe are defined to show similar weaknesses that the user may want to explore.
    + Relevant to the view "Research Concepts" (View-1000)
    Nature Type ID Name
    ChildOf Class Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource. 610 Externally Controlled Reference to a Resource in Another Sphere
    PeerOf Class Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource. 441 Unintended Proxy or Intermediary ('Confused Deputy')
    + Relevant to the view "Software Development" (View-699)
    Nature Type ID Name
    MemberOf Category Category - a CWE entry that contains a set of other entries that share a common characteristic. 19 Data Processing Errors
    + Relevant to the view "Weaknesses for Simplified Mapping of Published Vulnerabilities" (View-1003)
    Nature Type ID Name
    ChildOf Class Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource. 610 Externally Controlled Reference to a Resource in Another Sphere
    + Relevant to the view "Architectural Concepts" (View-1008)
    Nature Type ID Name
    MemberOf Category Category - a CWE entry that contains a set of other entries that share a common characteristic. 1015 Limit Access
    + 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
    Section HelpThe different Modes of Introduction provide information about how and when this weakness may be introduced. The Phase identifies a point in the life cycle at which introduction may occur, while the Note provides a typical scenario related to introduction during the given phase.
    Phase Note
    Implementation REALIZATION: This weakness is caused during implementation of an architectural security tactic.
    + Applicable Platforms
    Section HelpThis listing shows possible areas for which the given weakness could appear. These may be for specific named Languages, Operating Systems, Architectures, Paradigms, Technologies, or a class of such platforms. The platform is listed along with how frequently the given weakness appears for that instance.
    Languages

    Class: Not Language-Specific (Undetermined Prevalence)

    XML (Undetermined Prevalence)

    Technologies

    Class: Not Technology-Specific (Undetermined Prevalence)

    Class: Web Based (Undetermined Prevalence)

    + Selected Observed Examples

    Note: this is a curated list of examples for users to understand the variety of ways in which this weakness can be introduced. It is not a complete list of all CVEs that are related to this CWE entry.

    Reference Description
    Recruiter software allows reading arbitrary files using XXE
    A browser control can allow remote attackers to determine the existence of files via Javascript containing XML script.
    XXE during SVG image conversion
    XXE in PHP application allows reading the application's configuration file.
    XXE in database server
    XXE in rapid web application development framework allows reading arbitrary files.
    XXE via XML-RPC request.
    XXE in office document product using RDF.
    XXE in web-based administration tool for database.
    XXE in product that performs large-scale data analysis.
    XXE in XSL stylesheet functionality in a common library used by some web browsers.
    + Weakness Ordinalities
    Ordinality Description
    Primary
    (where the weakness exists independent of other weaknesses)
    + Detection Methods
    Method Details

    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
    + Memberships
    Section HelpThis MemberOf Relationships table shows additional CWE Categories and Views that reference this weakness as a member. This information is often useful in understanding where a weakness fits within the context of external information sources.
    Nature Type ID Name
    MemberOf CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. 990 SFP Secondary Cluster: Tainted Input to Command
    MemberOf CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. 1030 OWASP Top Ten 2017 Category A4 - XML External Entities (XXE)
    MemberOf ViewView - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries). 1200 Weaknesses in the 2019 CWE Top 25 Most Dangerous Software Errors
    MemberOf CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. 1308 CISQ Quality Measures - Security
    MemberOf ViewView - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries). 1337 Weaknesses in the 2021 CWE Top 25 Most Dangerous Software Weaknesses
    MemberOf ViewView - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries). 1340 CISQ Data Protection Measures
    MemberOf CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. 1349 OWASP Top Ten 2021 Category A05:2021 - Security Misconfiguration
    MemberOf ViewView - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries). 1350 Weaknesses in the 2020 CWE Top 25 Most Dangerous Software Weaknesses
    MemberOf ViewView - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries). 1387 Weaknesses in the 2022 CWE Top 25 Most Dangerous Software Weaknesses
    MemberOf CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. 1396 Comprehensive Categorization: Access Control
    MemberOf CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. 1437 OWASP Top Ten 2025 Category A02:2025 - Security Misconfiguration
    + Vulnerability Mapping Notes
    Usage ALLOWED
    (this CWE ID may be used to map to real-world vulnerabilities)
    Reason Acceptable-Use

    Rationale

    		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.

    Comments

    		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.
    + Notes

    Relationship

    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.
    + Taxonomy Mappings
    Mapped Taxonomy Name Node ID Fit Mapped Node Name
    WASC 43 XML External Entities
    Software Fault Patterns SFP24 Tainted input to command
    + References
    [REF-496] OWASP. "XML External Entity (XXE) Processing".
    <https://www.owasp.org/index.php/XML_External_Entity_(XXE)_Processing>.
    [REF-497] Sascha Herzog. "XML External Entity Attacks (XXE)". 2010-10-20.
    <https://mohemiv.com/files/XML_Exteral_Entity_Attack.pdf>. (URL validated: 2025-07-29)
    [REF-498] Gregory Steuck. "XXE (Xml eXternal Entity) Attack".
    <https://seclists.org/bugtraq/2002/Oct/420/>. (URL validated: 2025-07-29)
    [REF-499] WASC. "XML External Entities (XXE) Attack".
    <http://projects.webappsec.org/w/page/13247003/XML%20External%20Entities>.
    [REF-500] Bryan Sullivan. "XML Denial of Service Attacks and Defenses". 2009-09.
    <https://learn.microsoft.com/en-us/archive/msdn-magazine/2009/november/xml-denial-of-service-attacks-and-defenses>. (URL validated: 2023-04-07)
    [REF-501] Chris Cornutt. "Preventing XXE in PHP".
    <https://websec.io/2012/08/27/Preventing-XXE-in-PHP.html>. (URL validated: 2023-04-07)
    + Content History
    + Submissions
    Submission Date Submitter Organization
    2007-05-07
    (CWE Draft 6, 2007-05-07)     		Anonymous Tool Vendor (under NDA)
    + Modifications
    Modification Date Modifier Organization
    2025-12-11
    (CWE 4.19, 2025-12-11)     		CWE Content Team MITRE
    updated Applicable_Platforms, Background_Details, Common_Consequences, Description, Diagram, Relationships, Weakness_Ordinalities
    2025-09-09
    (CWE 4.18, 2025-09-09)     		CWE Content Team MITRE
    updated References
    2023-10-26
    (CWE 4.13, 2023-10-26)     		CWE Content Team MITRE
    updated Observed_Examples
    2023-06-29
    (CWE 4.12, 2023-06-29)     		CWE Content Team MITRE
    updated Mapping_Notes
    2023-04-27
    (CWE 4.11, 2023-04-27)     		CWE Content Team MITRE
    updated Detection_Factors, References, Relationships
    2023-01-31
    (CWE 4.10, 2023-01-31)     		CWE Content Team MITRE
    updated Alternate_Terms, Common_Consequences, Description
    2022-06-28
    (CWE 4.8, 2022-06-28)     		CWE Content Team MITRE
    updated Relationships
    2021-10-28
    (CWE 4.6, 2021-10-28)     		CWE Content Team MITRE
    updated Relationships
    2021-07-20
    (CWE 4.5, 2021-07-20)     		CWE Content Team MITRE
    updated Relationships
    2020-12-10
    (CWE 4.3, 2020-12-10)     		CWE Content Team MITRE
    updated Relationships
    2020-08-20
    (CWE 4.2, 2020-08-20)     		CWE Content Team MITRE
    updated Relationships
    2020-02-24
    (CWE 4.0, 2020-02-24)     		CWE Content Team MITRE
    updated Applicable_Platforms, Relationships
    2019-09-19
    (CWE 3.4, 2019-09-19)     		CWE Content Team MITRE
    updated Relationships
    2019-06-20
    (CWE 3.3, 2019-06-20)     		CWE Content Team MITRE
    updated Name, Type
    2019-01-03
    (CWE 3.2, 2019-01-03)     		CWE Content Team MITRE
    updated Related_Attack_Patterns
    2018-03-27
    (CWE 3.1, 2018-03-27)     		CWE Content Team MITRE
    updated Relationships
    2017-11-08
    (CWE 3.0, 2017-11-08)     		CWE Content Team MITRE
    updated Modes_of_Introduction, References, Relationships, Relevant_Properties
    2015-12-07
    (CWE 2.9, 2015-12-07)     		CWE Content Team MITRE
    updated Relationships
    2014-07-30
    (CWE 2.8, 2014-07-31)     		CWE Content Team MITRE
    updated Relationships, Taxonomy_Mappings
    2013-02-21
    (CWE 2.4, 2013-02-21)     		CWE Content Team MITRE
    updated Alternate_Terms, Applicable_Platforms, Background_Details, Common_Consequences, Description, Name, Observed_Examples, Potential_Mitigations, References, Relationship_Notes, Relationships, Taxonomy_Mappings
    2012-05-11
    (CWE 2.2, 2012-05-15)     		CWE Content Team MITRE
    updated Relationships
    2011-06-01
    (CWE 1.13, 2011-06-01)     		CWE Content Team MITRE
    updated Common_Consequences
    2011-03-29
    (CWE 1.12, 2011-03-30)     		CWE Content Team MITRE
    updated Name
    2010-09-27
    (CWE 1.10, 2010-09-27)     		CWE Content Team MITRE
    updated Background_Details, Other_Notes
    2010-02-16
    (CWE 1.8, 2010-02-16)     		CWE Content Team MITRE
    updated Taxonomy_Mappings
    2008-09-08
    (CWE 1.0, 2008-09-09)     		CWE Content Team MITRE
    updated Description, Relationships, Observed_Example, Other_Notes, Taxonomy_Mappings
    2008-07-01
    (CWE 1.0, 2008-09-09)     		Eric Dalci Cigital
    updated Time_of_Introduction
    + Previous Entry Names
    Change Date Previous Entry Name
    2019-06-20 Improper Restriction of XML External Entity Reference ('XXE')
    2013-02-21 Information Exposure Through XML External Entity Reference
    2011-03-29 Information Leak Through XML External Entity File Disclosure
    Page Last Updated: April 30, 2026