If there was, DSiWarehax would be a moot point and 11.4 wouldn't need sighax to be hackable.
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I'm assuming you mean "how do you use DSiWarehax to install this on 11.4".
You buy and download a DSiWare game from the eShop on a 3DS with CFW. You then use GodMode9 to inject an exploitable game and its exploited save into NAND. Then, (after making a NAND backup on your CFW console to restore later) you do a System Transfer to the 11.4 console to move the exploited DSiWare to the unhacked console.
DSiWare has access to NAND, so at that point you can write sighax to your NAND using the same general exploit that a hardmod would use.
Doing a system transfer moves over your NNID from the source console, so it's not without its negatives.