Ripple uses substantially the same signature scheme as Bitcoin does and the server validates signatures similarly using OpenSSL. But Ripple doesn't require you to refer to previous transactions by ID to spend from them. So you can't prevent people from spending funds or jam their transaction chains.

The Ripple server will soon enforce fully canonical signatures on transactions and validations to ensure that no such attack is possible.

Ripple Labs Chief Cryptographer David Schwartz provided details on Ripple transaction malleability in an interview at Newfination.