complexities of attacks on MD5 and SHA-1 posted January 2016
Taken from the SLOTH paper, the current estimated complexities of the best known attacks against MD5 and SHA-1:
|Common-prefix collision||Chosen-prefix collision|
MD5|SHA-1 is a concatenation of the outputs of both hashes on the same input. It is a technique aimed at reducing the efficiency of these attacks, but as you can see it, it is not that efficient.