Something that looks like a good thing at first, but has unforeseen bad consequences.
For instance, while irrigation schemes provide people with water for agriculture, they can increase waterborne diseases that have devastating health effects, such as schistosomiasis. (From wikipedia)
Major edit in body to provide a better example as requested in the comments. Saeid, please let us know if you disagree and this conflicts with your intent. -T.R.
Best Answer
In certain contexts, a poisoned chalice works.
When something is a curse in disguise (in the disguise of a blessing), you can also simply say that something is more of a curse than a blessing.