A new leaked Jelly Bean ROM can be used on some variants of the international HTC One X smartphone. Here's a quote with the details,

Recognized XDA contributor Football has posted the custom ROM just hours ago, but it already looks like one of the safest ways of getting an early sneak peek at Jelly Bean. There is one simple explanation for the port’s stability, with Football claiming that this is actually a leaked software package based on the shipping software of the soon to be released One X+.

Unfortunately, the maXimus v4.1 ROM with Android 4.1.1 and HTC Sense 4+ can only be flashed on certain versions of the international model of the One X. More precisely, you shouldn’t be trying out the firmware if you don’t have a One X powered by NVIDIA’s Tegra 3 quad-core processor and if your CID number is not one of the following:
  • cidnum: HTC__001
  • cidnum: HTC__E11
  • cidnum: HTC__203
  • cidnum: HTC__102
  • cidnum: HTC__405
  • cidnum: HTC__Y13
  • cidnum: HTC__A07
  • cidnum: HTC__304
  • cidnum: HTC__M27
  • cidnum: HTC__032
  • cidnum: HTC__016
  • cidnum: HTC__J15

Now if you are one of the lucky owners of a “select” One X that can safely run the Jelly Bean-based custom ROM, you should take a very close look at the installing instructions at this link (right beneath the download). The usual set of precautions applies too, so be sure to back up your data before flashing and don’t forget that you’re pretty much guaranteed to void your phone’s warranty if you flash a custom ROM.
Here's a source link below if you want to give it a go. Just remember to follow all the instructions carefully so as not to brick your device.

XDA - ROM and Instructions Source

Source: AndroidAuthority