---
title: FML Security Error
description: "Minecraft's FML Security Error"
source: "https://nodecraft.com/support/games/minecraft/mods/fml-security-error"
image: "https://dynamic-assets.nodecraft.com/signedurl/w7vokBAexMnVlnMZ1Q/image.jpg?modifications=W3sibmFtZSI6ImdhbWVfYmciLCJpbWFnZV91cmwiOiJodHRwczovL2Ntcy1hLm5vZGVjcmFmdC5jb20vZi8xMzM5MzIvMjAwMHg1NTAvZGNiMGFkNjkzOC9jYXZlcy1hbmQtY2xpZmZzLXB0LTItMS0yLTAucG5nL20vIn0seyJuYW1lIjoiZ2FtZV9sb2dvIiwiaW1hZ2VfdXJsIjoiaHR0cHM6Ly9jbXMtYS5ub2RlY3JhZnQuY29tL2YvMTMzOTMyLzM3NXgxNTAvM2MxZGIyYmFiNS9taW5lY3JhZnQucG5nL20vIn0seyJuYW1lIjoiY3RhX3RleHQiLCJ0ZXh0IjoiQ3JlYXRlIHlvdXIgb3duIHNlcnZlciEifSx7Im5hbWUiOiJ0ZXh0IiwidGV4dCI6IkZNTCBTZWN1cml0eSBFcnJvciJ9XQ&s=184c5c16bdcea7684d81e28ce98ed7ae4424aebd08d637f4af063640f6f1571b"
published: "2018-06-09T03:22:28.147Z"
updated: "2020-02-10T22:54:00.000Z"
---

# FML Security Error

Minecraft's FML Security Error

If you have Forge installed in multiple locations, this can result in an FML security error, similiar to the one printed below. For example, this can occur if you have a `forge-14.23.4.2707.jar` jar in your primary directory, and then the same jar at `/mods/forge-14.23.4.2707.jar`.

`[main/ERROR] [LaunchWrapper]: Unable to launch
java.lang.RuntimeException: FML was unable to install the security manager. The game will not start
at net.minecraftforge.fml.common.launcher.FMLTweaker.<init>(FMLTweaker.java:58) ~[forge-14.23.4.2707.jar:?]
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) ~[?:1.8.0_171]
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62) ~[?:1.8.0_171]
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) ~[?:1.8.0_171]
at java.lang.reflect.Constructor.newInstance(Constructor.java:423) ~[?:1.8.0_171]
at java.lang.Class.newInstance(Class.java:442) ~[?:1.8.0_171]
at net.minecraft.launchwrapper.Launch.launch(Launch.java:98) [launchwrapper-1.12.jar:?]
at net.minecraft.launchwrapper.Launch.main(Launch.java:28) [launchwrapper-1.12.jar:?]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_171]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_171]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_171]
at java.lang.reflect.Method.invoke(Method.java:498) ~[?:1.8.0_171]
at net.minecraftforge.fml.relauncher.ServerLaunchWrapper.run(ServerLaunchWrapper.java:62) [forge-14.23.4.2707.jar:?]
at net.minecraftforge.fml.relauncher.ServerLaunchWrapper.main(ServerLaunchWrapper.java:31) [forge-14.23.4.2707.jar:?]
Caused by: java.lang.SecurityException: Cannot replace the FML security manager
at net.minecraftforge.fml.relauncher.FMLSecurityManager.checkPermission(FMLSecurityManager.java:54) ~[forge-14.23.4.2707.jar:?]
at java.lang.System.setSecurityManager0(System.java:300) ~[?:1.8.0_171]
at java.lang.System.setSecurityManager(System.java:291) ~[?:1.8.0_171]
at net.minecraftforge.fml.common.launcher.FMLTweaker.<init>(FMLTweaker.java:54) ~[forge-14.23.4.2707.jar:?]
... 13 more`

To resolve this error, remove the duplicate Forge jar, generally found in your `/mods` directory.