ACE vulnerability in JaninoEventEvaluator by QOS.CH logback-core upto including version 0.1 to 1.3.14 and 1.4.0 to 1.5.12 in Java applications allows attacker to execute arbitrary code by compromising an existing logback configuration file or by injecting an environment variable before program execution. Malicious logback configuration files can allow the attacker to execute arbitrary code using the JaninoEventEvaluator extension. A successful attack requires the user to have write access to a configuration file. Alternatively, the attacker could inject a malicious environment variable pointing to a malicious configuration file. In both cases, the attack requires existing privilege.
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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.