CWE - CWE-91: XML Injection (aka Blind XPath Injection) (4.20)

Weakness ID: 91

Vulnerability Mapping: ALLOWED This CWE ID could be used to map to real-world vulnerabilities in limited situations requiring careful review (with careful review of mapping notes)
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 does not properly neutralize special elements that are used in XML, allowing attackers to modify the syntax, content, or commands of the XML before it is processed by an end system.

Extended Description

Within XML, special elements could include reserved words or characters such as "<", ">", """, and "&", which could then be used to add new data or modify XML syntax.

Common Consequences

This 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
Execute Unauthorized Code or Commands; Read Application Data; Modify Application Data	Scope: Confidentiality, Integrity, Availability

Potential Mitigations

Phase(s)	Mitigation
Implementation	Strategy: Input Validation Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does. When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue." Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.

Phase(s)

Mitigation

Implementation

Strategy: Input Validation

Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.

When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue."

Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.

Relationships

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 - 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.	74	Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')
ParentOf	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.	643	Improper Neutralization of Data within XPath Expressions ('XPath Injection')
ParentOf	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.	652	Improper Neutralization of Data within XQuery Expressions ('XQuery Injection')

Relevant to the view "Software Development" (View-699)

Nature	Type	ID	Name
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	137	Data Neutralization Issues

Relevant to the view "Weaknesses for Simplified Mapping of Published Vulnerabilities" (View-1003)

Nature	Type	ID	Name
ChildOf	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.	74	Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')

Relevant to the view "Architectural Concepts" (View-1008)

Nature	Type	ID	Name
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1019	Validate Inputs

Modes Of Introduction

The 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

This 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)

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

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

This 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	Category - a CWE entry that contains a set of other entries that share a common characteristic.	713	OWASP Top Ten 2007 Category A2 - Injection Flaws
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	727	OWASP Top Ten 2004 Category A6 - Injection Flaws
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	810	OWASP Top Ten 2010 Category A1 - Injection
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	929	OWASP Top Ten 2013 Category A1 - Injection
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	990	SFP Secondary Cluster: Tainted Input to Command
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1027	OWASP Top Ten 2017 Category A1 - Injection
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1308	CISQ Quality Measures - Security
MemberOf	View - 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	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1347	OWASP Top Ten 2021 Category A03:2021 - Injection
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1409	Comprehensive Categorization: Injection
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1440	OWASP Top Ten 2025 Category A05:2025 - Injection

Vulnerability Mapping Notes

Usage

ALLOWED-WITH-REVIEW

(this CWE ID could be used to map to real-world vulnerabilities in limited situations requiring careful review)

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

This weakness might be confused with other weaknesses such as XXE. 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.

Suggestions

CWE-ID	Comment
CWE-611	XML External Entity (XXE)

Notes

Theoretical

In vulnerability theory terms, this is a representation-specific case of a Data/Directive Boundary Error.

Research Gap

Under-reported. This is likely found regularly by third party code auditors, but there are very few publicly reported examples.

Maintenance

The description for this entry is generally applicable to XML, but the name includes "blind XPath injection" which is more closely associated with CWE-643. Therefore this entry might need to be deprecated or converted to a general category - although injection into raw XML is not covered by CWE-643 or CWE-652.

Taxonomy Mappings

Mapped Taxonomy Name	Node ID	Fit	Mapped Node Name
PLOVER			XML injection (aka Blind Xpath injection)
OWASP Top Ten 2007	A2	CWE More Specific	Injection Flaws
OWASP Top Ten 2004	A6	CWE More Specific	Injection Flaws
WASC	23		XML Injection
Software Fault Patterns	SFP24		Tainted input to command

Related Attack Patterns

CAPEC-ID	Attack Pattern Name
CAPEC-250	XML Injection
CAPEC-83	XPath Injection

References

[REF-882]	Amit Klein. "Blind XPath Injection". 2004-05-19. <https://dl.packetstormsecurity.net/papers/bypass/Blind_XPath_Injection_20040518.pdf>. (URL validated: 2023-04-07)
[REF-62]	Mark Dowd, John McDonald and Justin Schuh. "The Art of Software Security Assessment". Chapter 17, "XML Injection", Page 1069. 1st Edition. Addison Wesley. 2006.

Content History

Submissions
Submission Date	Submitter	Organization
2006-07-19 (CWE Draft 3, 2006-07-19)	PLOVER
2006-07-19 (CWE Draft 3, 2006-07-19)
Modifications
Modification Date	Modifier	Organization
2026-04-30 (CWE 4.20, 2026-04-30)	CWE Content Team	MITRE
2026-04-30 (CWE 4.20, 2026-04-30)	updated Mapping_Notes
2025-12-11 (CWE 4.19, 2025-12-11)	CWE Content Team	MITRE
2025-12-11 (CWE 4.19, 2025-12-11)	updated Relationships, Weakness_Ordinalities
2023-06-29 (CWE 4.12, 2023-06-29)	CWE Content Team	MITRE
2023-06-29 (CWE 4.12, 2023-06-29)	updated Mapping_Notes
2023-04-27 (CWE 4.11, 2023-04-27)	CWE Content Team	MITRE
2023-04-27 (CWE 4.11, 2023-04-27)	updated Detection_Factors, References, Relationships, Time_of_Introduction
2023-01-31 (CWE 4.10, 2023-01-31)	CWE Content Team	MITRE
2023-01-31 (CWE 4.10, 2023-01-31)	updated Description
2021-10-28 (CWE 4.6, 2021-10-28)	CWE Content Team	MITRE
2021-10-28 (CWE 4.6, 2021-10-28)	updated Relationships
2020-12-10 (CWE 4.3, 2020-12-10)	CWE Content Team	MITRE
2020-12-10 (CWE 4.3, 2020-12-10)	updated Relationships
2020-08-20 (CWE 4.2, 2020-08-20)	CWE Content Team	MITRE
2020-08-20 (CWE 4.2, 2020-08-20)	updated Relationships
2020-06-25 (CWE 4.1, 2020-06-25)	CWE Content Team	MITRE
2020-06-25 (CWE 4.1, 2020-06-25)	updated Potential_Mitigations
2020-02-24 (CWE 4.0, 2020-02-24)	CWE Content Team	MITRE
2020-02-24 (CWE 4.0, 2020-02-24)	updated Potential_Mitigations, Related_Attack_Patterns, Relationships
2019-06-20 (CWE 3.3, 2019-06-20)	CWE Content Team	MITRE
2019-06-20 (CWE 3.3, 2019-06-20)	updated Related_Attack_Patterns
2018-03-27 (CWE 3.1, 2018-03-27)	CWE Content Team	MITRE
2018-03-27 (CWE 3.1, 2018-03-27)	updated Relationships
2017-11-08 (CWE 3.0, 2017-11-08)	CWE Content Team	MITRE
2017-11-08 (CWE 3.0, 2017-11-08)	updated Applicable_Platforms, Modes_of_Introduction, References, Relationships
2015-12-07 (CWE 2.9, 2015-12-07)	CWE Content Team	MITRE
2015-12-07 (CWE 2.9, 2015-12-07)	updated Relationships
2014-07-30 (CWE 2.8, 2014-07-31)	CWE Content Team	MITRE
2014-07-30 (CWE 2.8, 2014-07-31)	updated Relationships, Taxonomy_Mappings
2014-06-23 (CWE 2.7, 2014-06-23)	CWE Content Team	MITRE
2014-06-23 (CWE 2.7, 2014-06-23)	updated Relationships
2014-02-18 (CWE 2.6, 2014-02-19)	CWE Content Team	MITRE
2014-02-18 (CWE 2.6, 2014-02-19)	updated Related_Attack_Patterns
2012-10-30 (CWE 2.3, 2012-10-30)	CWE Content Team	MITRE
2012-10-30 (CWE 2.3, 2012-10-30)	updated Potential_Mitigations
2012-05-11 (CWE 2.2, 2012-05-15)	CWE Content Team	MITRE
2012-05-11 (CWE 2.2, 2012-05-15)	updated References, Relationships
2011-06-01 (CWE 1.13, 2011-06-01)	CWE Content Team	MITRE
2011-06-01 (CWE 1.13, 2011-06-01)	updated Common_Consequences
2010-06-21 (CWE 1.9, 2010-06-21)	CWE Content Team	MITRE
2010-06-21 (CWE 1.9, 2010-06-21)	updated Description, Relationships
2010-02-16 (CWE 1.8, 2010-02-16)	CWE Content Team	MITRE
2010-02-16 (CWE 1.8, 2010-02-16)	updated Taxonomy_Mappings
2008-10-14 (CWE 1.0.1, 2008-10-14)	CWE Content Team	MITRE
2008-10-14 (CWE 1.0.1, 2008-10-14)	updated Maintenance_Notes, Other_Notes, Theoretical_Notes
2008-09-08 (CWE 1.0, 2008-09-09)	CWE Content Team	MITRE
2008-09-08 (CWE 1.0, 2008-09-09)	updated Relationships, Other_Notes, Taxonomy_Mappings
2008-08-15 (CWE 1.0, 2008-09-09)		Veracode
2008-08-15 (CWE 1.0, 2008-09-09)	Suggested OWASP Top Ten 2004 mapping
2008-07-01 (CWE 1.0, 2008-09-09)	Eric Dalci	Cigital
2008-07-01 (CWE 1.0, 2008-09-09)	updated Time_of_Introduction

CWE Glossary Definition


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Common Weakness Enumeration

CWE-91: XML Injection (aka Blind XPath Injection)

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