OK, so... I'm attaching an update package which can disable (or re-enable) the vulnerability, until Amazon comes up with a proper patch.
To install the package, your device obviously needs to be jailbroken. Ironically, if needed, the jailbreak can be installed using the very vulnerability that this package fixes
EDIT: There's a typo in the README: Of course, the vulnerability isn't
triggered, but it (rather: its availability) is
toggled. Sorry for the potential confusion.
EDIT 2: This is obsolete. The vulnerability has been fixed with Firmware 5.1.2.