Synopsis
Version 6.43 of RouterOS included a changelog indicating:
!) winbox - improved authentication process excluding man-in-the-middle possibility;
The change involved the RouterOS WinBox interface (port 8291) switching the key agreement algorithm from a Diffie-Hellman implementation to an ECSRP-5 implementation. While the ECSRP-5 implementation is immune to man-in-the-middle attacks, a man in the middle can still downgrade the WinBox client to the Diffie-Hellman implementation. After the DH key exchange the client will send the attacker their username and the their MD5 hashed password (the hash is salted with an attacker defined salt).
A proof of concept has been uploaded to our research GitHub repository.
Solution
As of publication time, no solution currently exists.Additional References
https://www.cybersecurity-help.cz/vdb/SB2018091103https://github.com/tenable/routeros/blob/master/poc/cve_2019_3981/winbox_server.py
Disclosure Timeline
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