So, I downloaded the SFX archive from MajorGeeks (EUropean french link), and I get the following hashes :
EXE (size : 99 818 163 octets bytes) :
* MD5 : 3018117409E67F7728A64ED2C1FD9C3D
* SHA-1 : 05B22D58CFA781B9B6E4CE2500B4DC89C16284B9
ISO ( size : 129 351 680 octets bytes) :
* MD5 : ACD910E5143FFE72305071302DF8C32F
* SHA-1 : 9601CCD39F583BEBF95C39A94C7A032796EB63DD
Extracting the archive works fine, and so guess it's not corrupted.
Yet on the UBCD download page it still says :
ISO image
115MB [MD5 ] cfed7ac541890d26dc863cdb4489862c
[SHA1] 5b0e496ab6c32ef736b235a4c0bc289cc8731109
Self-extracting EXE
87MB [MD5 ] f244281ec6310a90780e730f0b073d5a
[SHA1] cbd4ad281200c9210e9343e344652d6840d8e6d9