CWE-917

Base Abstraction Level
Pillar — Highest-level weakness category
Class — Abstract, language-independent
Base — Specific enough to detect
Variant — Tied to specific technology
Compound — Requires multiple weaknesses Incomplete MITRE CWE Status
Stable — Fully reviewed and complete
Draft — Under development, may change
Incomplete — Partially defined by MITRE
Deprecated — No longer recommended
Obsolete — Replaced by another CWE
Improper Neutralization of Special Elements used in an Expression Language Statement ('Expression Language Injection')

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.

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.

Top Monitored CVEs

CVE-2021-44228
CRITICAL KEV
10.0 100.0%
2021-12-10
CVE-2021-26084
CRITICAL KEV
9.8 100.0%
2021-08-30
CVE-2022-26134
CRITICAL KEV
9.8 100.0%
2022-06-03
CVE-2021-45046
CRITICAL KEV
9.0 100.0%
2021-12-14
CVE-2022-22963
CRITICAL KEV
9.8 99.9%
2022-04-01
CVE-2020-10199
HIGH KEV
8.8 99.1%
2020-04-01
CVE-2022-22947
CRITICAL KEV
10.0 98.3%
2022-03-03
CVE-2020-17530
CRITICAL KEV
9.8 95.9%
2020-12-11
CVE-2025-41243
CRITICAL
10.0 3.3%
2025-09-16
CVE-2023-41331
CRITICAL
9.8 1.3%
2023-09-12

Consequences

Confidentiality — Read Application Data
Integrity — Execute Unauthorized Code or Commands

Mitigations

Phase: Architecture and Design

Avoid adding user-controlled data into an expression interpreter when possible.

Phase: 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

Phase: 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".

Detection

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.)