In the Linux kernel, the following vulnerability has been resolved:

ksmbd: defer destroy_previous_session() until after NTLM authentication

In ntlm_authenticate(), destroy_previous_session() is called using a
user pointer resolved from the client-supplied NTLM blob username field
before the NTLMv2 response is validated. An authenticated attacker can
set the NTLM blob username to match a victim account and set
PreviousSessionId to the victim's session ID; destroy_previous_session()
destroys the victim's session while ksmbd_decode_ntlmssp_auth_blob()
subsequently rejects the request with -EPERM.

Move destroy_previous_session() and the prev_id assignment to after
ksmbd_decode_ntlmssp_auth_blob() returns success and use sess->user
rather than the pre-authentication lookup result. This matches the
ordering already used by krb5_authenticate(), where
destroy_previous_session() is called only after
ksmbd_krb5_authenticate() returns success.