If you are between 11.0.0 and 11.2.0, you must follow this guide to downgrade your NFIRM using one of the methods at the bottom of this page to directly dump and restore your NAND.
All of these are working implementation of the "FIRM partitions known-plaintext" exploit detailed [here](https://www.3dbrew.org/wiki/3DS_System_Flaws).
+ Use [this](hardmod-downgrade) link to downgrade your NFIRM with a [hardmod](https://gbatemp.net/threads/414498/)
+ Use [this](dsiware-downgrade-(app-injection-and-second-3ds)) link to downgrade your NFIRM with DSiWare and a second 3DS (which already has CFW)
+ Use [this](dsiware-downgrade-(save-injection)) link to downgrade your NFIRM with DSiWare, one of four listed games, and a homebrew launcher entrypoint *(11.0.0 and 11.1.0 only)*
+ Use [this](dsiware-downgrade-(save-injection-and-second-3ds)) link to downgrade your NFIRM with DSiWare, one of four listed games, and a second 3DS (which already has CFW)