Is ElGamal IND-CCA1?
The CCA1 security of ElGamal is a big open question. There are no attacks known, but standard reductions don't seem to work. 

In 1991, Damgard proposed an ElGamal variant and proved it to be CCA1-secure (albeit under a very problematic non-falsifiable assumption, called the "knowledge of exponent assumption"); see the paper here http://link.springer.com/chapter/10.1007%2F3-540-46766-1_36. 

More recently, Lipmaa here showed that ElGamal can be proven to be CCA1-secure under a non-standard (but falsifiable) assumption. The assumption is that DDH is hard even given access to a static CDH oracle (that computes the Diffie-Hellman function for a fixed "secret" exponent). [Caveat: I haven't read the paper so I can't vouch for correctness...]