Input Validation / Expression Language Injection

Web and API


Expression Language (EL) injection is a type of vulnerability that occurs when an attacker is able to inject malicious code into an application's expression language interpreter (ELI). EL injection attacks can be used to gain access to sensitive data, modify existing data, and execute arbitrary commands. EL injection is also known as Expression Language Injection, ELI Injection, and Expression Injection. According to the Common Weakness Enumeration (CWE) directory, EL injection is classified as a type of input validation vulnerability (CWE-913). EL injection can occur in web applications or API's and is included in the OWASP Testing Guide as a category of injection attacks.


Expression Language injection can present significant risk to an application. Exploiting this vulnerability can lead to data theft, data loss, or even system compromise. An attacker can use EL injection to bypass authentication, access sensitive data, and execute malicious code on the application's server. Poorly configured security settings, inadequate input validation and authentication, and usage of outdated software can give attackers the opportunity to launch EL injection attacks.


The best way to protect against EL injection attacks is to use a secure development process and to validate all user input. All user input should be validated against a whitelist of expected characters and data types, and any potentially malicious code should be sanitized and encoded prior to being passed to the EL interpreter. Additionally, proper authentication and authorization should be implemented and updated regularly.

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