Is cryptanalysis of CTB-Locker really impossible? It seems that CTB-Locker make a lot of victims nowadays, and yet, the full encryption scheme of it is now publicly known [1,2]. 

Would any of you could find a weakness to exploit in this encryption scheme that would be able to take it down once for all ? The point would be to recover the Master key or a way to circumvent the encryption.

See also: 


« Where to find a full analysis of the encryption scheme of CTB-Locker? » on Reverse-engineering Stack-Exchange.
« Decrypt files with original file CTB-Locker », another question about CTB-Locker on Cryptography Stack-Exchange.
No. One of the most important principles of cryptography is that knowing the encryption scheme cannot help someone attempting to decrypt the material without the key. The encryption used seems to be a reasonably well-written implementation of several standard algorithms, for which no practical attacks are known. Finding a way to crack these would be a major undertaking, one which many skilled cryptographers have already failed at.