CVE-2020-10693: 
Java vulnerability analysis and mitigation

CVE-2020-10693 is a security vulnerability discovered in Hibernate Validator version 6.1.2.Final. The vulnerability was identified in the message interpolation processor, which incorrectly enables invalid EL (Expression Language) expressions to be evaluated as if they were valid (NVD, GitHub Security Lab).

The vulnerability stems from a bug in the message interpolation parser (org.hibernate.validator.internal.engine.messageinterpolation.parser.TokenCollector) that allows attackers to bypass input sanitation controls. When the parser encounters specific character sequences like 'FOO $\A{payload}', it incorrectly processes the tokens, effectively replacing '{' with '${' and marking it as an EL token. The vulnerability has been assigned a CVSS v3.1 Base Score of 5.3 (Medium) with vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N (GitHub Security Lab, NVD).

This vulnerability enables attackers to bypass input sanitation (escaping, stripping) controls that developers may have implemented when handling user-controlled data in error messages. In affected applications, this could potentially lead to remote code execution through malicious EL expressions (GitHub Security Lab).

The vulnerability can be exploited remotely without requiring authentication or user interaction. The attack complexity is considered low, as it primarily involves crafting specific input patterns that can bypass the existing input sanitation controls (NVD).

The vulnerability has been fixed in Hibernate Validator versions 6.1.5.Final, 6.0.20.Final, and 7.0.0.Alpha2. As a workaround before applying patches, developers can pass user input as an expression variable by unwrapping the context to HibernateConstraintValidatorContext (Red Hat Bugzilla).