Samba 3.x and 4.x before 4.1.22, 4.2.x before 4.2.7, and 4.3.x before 4.3.3 supports connections that are encrypted but unsigned, which allows man-in-the-middle attackers to conduct encrypted-to-unencrypted downgrade attacks by modifying the client-server data stream, related to clidfs.c, libsmb_server.c, and smbXcli_base.c.
Exploitability
AV:NAC:HPR:NUI:NScope
S:CImpact
C:LI:LA:N5.4/CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:N