CVE-2020-10693 in Middleware Common Libraries and Tools
Summary
by MITRE
A flaw was found in Hibernate Validator version 6.1.2.Final. A bug in the message interpolation processor enables invalid EL expressions to be evaluated as if they were valid. This flaw allows attackers to bypass input sanitation (escaping, stripping) controls that developers may have put in place when handling user-controlled data in error messages.
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Analysis
by VulDB Data Team • 09/13/2025
The vulnerability identified as CVE-2020-10693 resides within the Hibernate Validator framework, specifically in version 6.1.2.Final, representing a critical security flaw that undermines the integrity of input validation mechanisms. This issue manifests through a defect in the message interpolation processor component that governs how validation error messages are constructed and displayed to users. The flaw operates by permitting the execution of malformed expression language expressions that would typically be rejected by proper validation protocols, thereby creating a pathway for malicious input to bypass intended security controls.
The technical nature of this vulnerability stems from insufficient validation of expression language expressions within the message interpolation process. When developers implement input sanitization measures to protect against cross-site scripting and other injection attacks, these protections become ineffective if the validation framework itself fails to properly validate the expressions used in error message construction. The flaw essentially allows attackers to craft input that, while appearing valid to the application's user interface, contains embedded EL expressions that execute with elevated privileges within the context of the message interpolation processor. This creates a scenario where attackers can manipulate the validation framework to execute arbitrary code or access restricted functionality.
The operational impact of CVE-2020-10693 extends beyond simple bypassing of input sanitization controls, as it represents a fundamental weakness in the validation pipeline that can be exploited across multiple attack vectors. Applications utilizing Hibernate Validator for form validation, API request processing, and user input handling become vulnerable to code injection attacks that can potentially lead to remote code execution or data exfiltration. The vulnerability particularly affects systems where user input is directly incorporated into validation error messages without proper sanitization, creating a persistent threat that can be exploited by attackers who understand the application's validation patterns and message interpolation mechanisms. This flaw aligns with CWE-94, which describes "Improper Control of Generation of Code ('Code Injection')" and can be mapped to ATT&CK technique T1059.007 for "Command and Scripting Interpreter: Python" or similar execution techniques depending on the target environment.
Mitigation strategies for CVE-2020-10693 require immediate patching of the Hibernate Validator library to version 6.1.3.Final or later, which contains the necessary fixes to properly validate expression language expressions during message interpolation. Organizations should also implement additional defensive measures including the restriction of user input in validation error messages, the implementation of comprehensive input sanitization at multiple layers, and the adoption of secure coding practices that prevent direct user-controlled data from being used in expression language contexts. Security teams should conduct thorough code reviews to identify any custom validation logic that might be vulnerable to similar exploitation patterns and consider implementing runtime monitoring to detect anomalous expression evaluation patterns that could indicate attempted exploitation of this vulnerability. The fix addresses the root cause by strengthening the validation of expression language expressions and ensuring that only properly formatted and validated expressions are processed within the message interpolation framework, thereby restoring the intended security controls that protect against malicious input manipulation.