Intermission: Notes on the potential
Traditional japanese grammar says that the passive and potential are blurry in general, even for five-form verbs, but it's only a matter of time before they're not. A doubled-up form, as in 食べれられる, is already in very common colloquial use. I've been told it's feminine.
In any case, if you see one of the five-form potentials or the one-form short potential, you can be 99.9999% sure it doesn't mean the passive.
The short potential is sometimes homophonous with an existing strictly "passive" intransitive verb that comes from the same root transitive word, like 切れる. In these cases, you just have to stay frosty.
The five-form verbs' potential form might come from the stem used with the polite (ます) form, plus 得る える, a verb that normally means "get" but here means "is possible". The -ie sequence would contract to -e, except for ありえる.
As a side note, the five-form -eru potentials predate the one-form short potential, which is probably why they're more accepted.