The auth_via_key function in pam_ssh.c in pam_ssh before 1.92, when the allow_blank_passphrase option is disabled, allows remote attackers to bypass authentication restrictions and use private encryption keys requiring a blank passphrase by entering a non-blank passphrase.
Exploitability
AV:NAC:LAu:NImpact
C:PI:PA:N6.4/AV:N/AC:L/Au:N/C:P/I:P/A:N