A flaw has been found in antlr ANTLR4 up to 4.13.2. This affects the function ObjectInputStream.readObject of the file antlr4-maven-plugin/src/main/java/org/antlr/mojo/antlr4/GrammarDependencies.java of the component Maven Plugin. This manipulation causes time-of-check time-of-use. The attack is restricted to local execution. A high degree of complexity is needed for the attack. It is indicated that the exploitability is difficult. The exploit has been published and may be used. The vendor was contacted early about this disclosure but did not respond in any way.