CWE - CWE-917: Improper Neutralization of Special Elements used in an Expression Language Statement ('Expression Language Injection') (4.20)
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    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
    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
    + 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
    MemberOf CategoryCategory - 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
    (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". 2011-09-12.
    <https://mindedsecurity.com/wp-content/uploads/2020/10/ExpressionLanguageInjection.pdf>. (URL validated: 2023-04-07)
    [REF-912] Dan Amodio. "Remote Code with Expression Language Injection". 2012-12-14.
    <http://danamodio.com/appsec/research/spring-remote-code-with-expression-language-injection/>. (URL validated: 2023-04-07)
    [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
    2013-02-15
    (CWE 2.4, 2013-02-21)     		CWE Content Team MITRE
    + Contributions
    Contribution Date Contributor Organization
    2013-02-15 Dan Amodio, Dave Wichers Aspect Security
    Suggested adding this weakness and provided references.
    + Modifications
    Modification Date Modifier Organization
    2025-12-11
    (CWE 4.19, 2025-12-11)     		CWE Content Team MITRE
    updated Relationships
    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 Description
    2022-06-28
    (CWE 4.8, 2022-06-28)     		CWE Content Team MITRE
    updated Description, Maintenance_Notes, Observed_Examples, Potential_Mitigations, References, 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 References
    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 Relationships
    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 References
    Page Last Updated: April 30, 2026