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.
View on MITREFrameworks 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.
Avoid adding user-controlled data into an expression interpreter when possible.
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
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".
No detection method information available for this CWE.
Product does not neutralize ${xyz} style expressions, allowing remote code execution. (log4shell vulnerability in log4j)
View DetailsNo relationship information available for this CWE.
CWE-917: Improper Neutralization of Special Elements used in an Expression Language Statement ('Expression Language Injection') is a Common Weakness Enumeration (CWE) entry maintained by MITRE. 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.
If exploited, CWE-917 (Improper Neutralization of Special Elements used in an Expression Language Statement ('Expression Language Injection')) it can compromise Confidentiality and Integrity, leading to outcomes such as Read Application Data and Execute Unauthorized Code or Commands.
Recommended mitigations for CWE-917 include: Avoid adding user-controlled data into an expression interpreter when possible. 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 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".
CWE-917 commonly affects Java. Note that weaknesses are often language-agnostic patterns, so secure coding practices apply broadly.
MITRE documents real CVEs mapped to CWE-917, including CVE-2021-44228. You can look up the full details of each CVE, including CVSS scores and remediation guidance, on our CVE Lookup tool.
A CWE (Common Weakness Enumeration) like CWE-917 describes a category of software weakness — the underlying flaw type. A CVE (Common Vulnerabilities and Exposures) identifies a specific, real-world vulnerability in a particular product. In short, a CWE is the kind of mistake, and a CVE is an instance of that mistake being found in software.