Terrapin-Attack Style Vulnerability Likely Exploited for 2 Years

I wanted to share some insights into a security concern that echoes the Terrapin-Attack scenario, highlighting a similar vulnerability that has been observed in other tools.

Recently, I came across a Pull Request on GitHub for the SSH-MITM tool, which sheds light on a critical aspect of SSH protocol security, specifically regarding RFC 4253 during the KEXINIT process. The Pull Request, available at GitHub https://github.com/ssh-mitm/ssh-mitm/pull/163, describes the necessity of discarding certain packages during the KEXINIT phase to prevent issues with intercepted clients.

Moreover, a look into the GitHub Blame for SSH-MITM reveals that these crucial changes in the KEXINIT step were integrated into SSH-MITM about 1-2 years ago. You can see the specific changes at this link: https://github.com/ssh-mitm/ssh-mitm/blame/4fc3ef418847c35d17d0c427e2701b33a03c323c/sshmitm/workarounds/transport.py#L178-L188

An important note to add is that this information suggests that a similar form of attack, akin to the Terrapin-Attack, could potentially have been exploited for the last two years. This raises significant concerns about the historical vulnerability of systems to such attack techniques and emphasizes the importance of retroactive security analysis in addition to ongoing vigilance.