CWE - CWE-917: Improper Neutralization of Special Elements used in an Expression Language Statement ('Expression Language Injection') (4.18)

Home > CWE List > CWE-917: Improper Neutralization of Special Elements used in an Expression Language Statement ('Expression Language Injection') (4.18)

CWE Glossary Definition

CWE-917: Improper Neutralization of Special Elements used in an Expression Language Statement ('Expression Language Injection')

Weakness ID: 917

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 constructs all or part of an expression language (EL) statement in a framework such as a Java Server Page (JSP) using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended EL statement before it is executed.

Extended Description

Frameworks such as Java Server Page (JSP) allow a developer to insert executable expressions within otherwise-static content. When the developer is not aware of the executable nature of these expressions and/or does not disable them, then if an attacker can inject expressions, this could lead to code execution or other unexpected behaviors.

Alternate Terms

EL Injection

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	Scope: Confidentiality
Execute Unauthorized Code or Commands	Scope: Integrity

Potential Mitigations

Phase(s)	Mitigation
Architecture and Design	Avoid adding user-controlled data into an expression interpreter when possible.
Implementation	If user-controlled data must be added to an expression interpreter, one or more of the following should be performed: Validate that the user input will not evaluate as an expression Encode the user input in a way that ensures it is not evaluated as an expression
System Configuration; Operation	The framework or tooling might allow the developer to disable or deactivate the processing of EL expressions, such as setting the isELIgnored attribute for a JSP page to "true".

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.	77	Improper Neutralization of Special Elements used in a Command ('Command Injection')
PeerOf	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.	1336	Improper Neutralization of Special Elements Used in a Template Engine

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.	137	Data Neutralization Issues

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.	74	Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')

Relevant to the view "CISQ Quality Measures (2020)" (View-1305)

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.	77	Improper Neutralization of Special Elements used in a Command ('Command Injection')

Relevant to the view "CISQ Data Protection Measures" (View-1340)

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.	77	Improper Neutralization of Special Elements used in a Command ('Command Injection')

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
Architecture and Design
Implementation

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

Java (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
CVE-2021-44228	Product does not neutralize ${xyz} style expressions, allowing remote code execution. (log4shell vulnerability in log4j)

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

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.	1027	OWASP Top Ten 2017 Category A1 - Injection
MemberOf	CategoryCategory - 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	CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.	1409	Comprehensive Categorization: Injection

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

In certain versions of Spring 3.0.5 and earlier, there was a vulnerability (CVE-2011-2730) in which Expression Language tags would be evaluated twice, which effectively exposed any application to EL injection. However, even for later versions, this weakness is still possible depending on configuration.

Maintenance

The interrelationships and differences between CWE-917 and CWE-1336 need to be further clarified.

References

[REF-911] Stefano Di Paola and Arshan Dabirsiaghi. "Expression Language Injection". 2011年09月12日.
<https://mindedsecurity.com/wp-content/uploads/2020/10/ExpressionLanguageInjection.pdf>. (URL validated: 2023年04月07日)

[REF-912] Dan Amodio. "Remote Code with Expression Language Injection". 2012年12月14日.
<http://danamodio.com/appsec/research/spring-remote-code-with-expression-language-injection/>. (URL validated: 2023年04月07日)

[REF-1279] CWE/CAPEC. "Neutralizing Your Inputs: A Log4Shell Weakness Story".
<https://medium.com/@CWE_CAPEC/neutralizing-your-inputs-a-log4shell-weakness-story-89954c8b25c9>.

[REF-1280] OWASP. "Expression Language Injection".
<https://owasp.org/www-community/vulnerabilities/Expression_Language_Injection>.

Content History

Submissions
Submission Date	Submitter	Organization
2013年02月15日 (CWE 2.4, 2013年02月21日)	CWE Content Team	MITRE
2013年02月15日 (CWE 2.4, 2013年02月21日)
Contributions
Contribution Date	Contributor	Organization
2013年02月15日	Dan Amodio, Dave Wichers	Aspect Security
2013年02月15日	Suggested adding this weakness and provided references.
Modifications
Modification Date	Modifier	Organization
2023年06月29日	CWE Content Team	MITRE
2023年06月29日	updated Mapping_Notes
2023年04月27日	CWE Content Team	MITRE
2023年04月27日	updated Detection_Factors, References, Relationships
2023年01月31日	CWE Content Team	MITRE
2023年01月31日	updated Description
2022年06月28日	CWE Content Team	MITRE
2022年06月28日	updated Description, Maintenance_Notes, Observed_Examples, Potential_Mitigations, References, Relationships
2021年10月28日	CWE Content Team	MITRE
2021年10月28日	updated Relationships
2021年07月20日	CWE Content Team	MITRE
2021年07月20日	updated References
2020年12月10日	CWE Content Team	MITRE
2020年12月10日	updated Relationships
2020年08月20日	CWE Content Team	MITRE
2020年08月20日	updated Relationships
2020年02月24日	CWE Content Team	MITRE
2020年02月24日	updated Relationships
2018年03月27日	CWE Content Team	MITRE
2018年03月27日	updated Relationships
2017年11月08日	CWE Content Team	MITRE
2017年11月08日	updated References

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Page Last Updated: September 09, 2025

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