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.
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.

Primary

EL Injection

Architecture and Design

Implementation

Confidentiality
Read Application Data

Integrity
Execute Unauthorized Code or Commands

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

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".

CVE-2021-44228
Product does not neutralize ${xyz} style expressions, allowing remote code execution. (log4shell vulnerability in log4j)
https://www.cve.org/CVERecord?id=CVE-2021-44228

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.

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

CWE Content Team
MITRE
2013-02-15
2.4
2013-02-21

CWE Content Team
MITRE
2017-11-08
updated References

CWE Content Team
MITRE
2018-03-27
updated Relationships

CWE Content Team
MITRE
2020-02-24
updated 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 References

CWE Content Team
MITRE
2021-10-28
updated Relationships

CWE Content Team
MITRE
2022-06-28
updated Description, Maintenance_Notes, Observed_Examples, Potential_Mitigations, References, Relationships

CWE Content Team
MITRE
2023-01-31
updated 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
2025-12-11
4.19
2025-12-11
updated Relationships

Dan Amodio, Dave Wichers
Aspect Security
2013-02-15
Suggested adding this weakness and provided references.