The PuTTY SSH client, which is widespread especially under Windows, is vulnerable and attackers may be able to remotely execute malicious code on computers. In addition to the Windows version, the output for Unix systems is also at risk. The secured version of PuTTY 0.71 is now available for download. It looks like all previous issues are vulnerable. In the changelog you can read that the developers have mainly worked on security functions. Among other things, they have closed five weak points. A classification of the threat level is not recorded in the changelog. However, since many attacks work remotely to execute malicious code on affected computers, a critical classification is assumed. For example, attackers could interfere with RSA key exchange before verification and overwrite memory with their own code. In addition, the Zufalsszahlengenrator is probably on recycling. On Windows, attackers could use a help file in the PuTTY-EXE folder for attacks. Under Unix, attacks in server-to-client forwarding are conceivable. In addition, attackers should be able to trigger DoS attacks via the terminal. Furthermore, the developers claim to have optimized the crypto code against side channel attacks. AES, SHA-1 and SHA-256 should now be computed with hardware accelerated.
As well as using Filezilla and WinSCP code from PuTTY, these too are threatened by some of these gaps. Filezilla has secured version 3.41.2. According to the bugtracker, WinSCP protects edition 5.13.9.