CVE-2020-9296 in Conductor
Summary
by MITRE
Netflix Conductor uses Java Bean Validation (JSR 380) custom constraint validators. When building custom constraint violation error messages, different types of interpolation are supported, including Java EL expressions. If an attacker can inject arbitrary data in the error message template being passed to ConstraintValidatorContext.buildConstraintViolationWithTemplate() argument, they will be able to run arbitrary Java code.
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Analysis
by VulDB Data Team • 06/17/2020
The vulnerability identified as CVE-2020-9296 resides within Netflix Conductor's implementation of Java Bean Validation (JSR 380) custom constraint validators. This system employs a sophisticated validation framework that supports multiple interpolation methods for constructing constraint violation error messages, including Java Expression Language (EL) expressions. The core flaw emerges from insufficient input sanitization when processing error message templates, creating a path for arbitrary code execution through carefully crafted malicious inputs.
The technical exploitation of this vulnerability leverages the Java Bean Validation framework's support for expression language interpolation, specifically targeting the ConstraintValidatorContext.buildConstraintViolationWithTemplate() method. When attackers can control the template parameter passed to this method, they gain the ability to inject Java EL expressions that execute arbitrary code within the application's runtime environment. This represents a critical security flaw that transforms a validation error reporting mechanism into a code execution vector, bypassing traditional input validation controls.
From an operational impact perspective, this vulnerability creates a severe risk for systems utilizing Netflix Conductor's validation infrastructure. The attack surface extends to any application component that relies on custom constraint validators and allows external input to influence error message templates. Successful exploitation could enable attackers to execute arbitrary commands, access sensitive data, or compromise the entire application environment, making this a high-severity vulnerability that affects enterprise systems relying on Conductor's validation framework.
The vulnerability aligns with CWE-94, which describes "Improper Control of Generation of Code ('Code Injection')" and demonstrates characteristics consistent with the ATT&CK technique T1059.007 for "Command and Scripting Interpreter: Python." The flaw essentially allows attackers to inject and execute arbitrary Java code through the validation system's interpolation mechanism, bypassing normal security controls. Organizations should implement strict input validation, sanitize all user-provided data before it reaches constraint violation template processing, and disable unnecessary EL expression support in validation contexts. Additionally, regular security audits of validation frameworks and constraint implementations should be conducted to identify similar injection vulnerabilities in custom validation logic.