Samba AD/PDC authentication stopped working after recent Windows updates

This document (000021140) is provided subject to the disclaimer at the end of this document.


SUSE Linux Enterprise Server 15 SP4 <= samba-4.15.13+git.636.53d93c5b9d6-150400.3.23.1


After recent Windows updates, authentication to Samba in AD/PDC mode stopped working.

Samba logs with debugging enabled reveal the following:
[2023/07/19 12:16:18.741049, 10, pid=22070, effective(0, 0), real(0, 0)] ../../librpc/rpc/server/netlogon/schannel_util.c:194(dcesrv_netr_check_schannel_once)
  CVE-2020-1472(ZeroLogon)/CVE-2022-38023: netr_LogonGetCapabilities request (opnum[21]) WITH SEALED schannel from client_account[FOOBAR$] client_computer_name[FOOBAR] NT_STATUS_OK
[2023/07/19 12:16:18.741062,  4, pid=22070, effective(65534, 65534), real(65534, 0)] ../../source3/smbd/sec_ctx.c:444(pop_sec_ctx)
  pop_sec_ctx (65534, 65534) - sec_ctx_stack_ndx = 1
[2023/07/19 12:16:18.741074,  4, pid=22070, effective(65534, 65534), real(65534, 0)] ../../source3/smbd/sec_ctx.c:444(pop_sec_ctx)
  pop_sec_ctx (65534, 65534) - sec_ctx_stack_ndx = 0
[2023/07/19 12:16:18.741082,  1, pid=22070, effective(65534, 65534), real(65534, 0), class=rpc_parse] ../../librpc/ndr/ndr.c:484(ndr_print_function_debug)
       netr_LogonGetCapabilities: struct netr_LogonGetCapabilities
          out: struct netr_LogonGetCapabilities
              return_authenticator     : *
                  return_authenticator: struct netr_Authenticator
                      cred: struct netr_Credential
                          data                     : cba8cc77246d671b
                      timestamp                : (time_t)0
              capabilities             : *
                  capabilities             : union netr_Capabilities(case 2)
                  UNKNOWN LEVEL 2
              result                   : NT_STATUS_NOT_SUPPORTED
[2023/07/19 12:16:18.741126,  1, pid=22070, effective(65534, 65534), real(65534, 0), class=rpc_parse] ../../librpc/ndr/ndr.c:666(_ndr_push_error)
  ndr_push_netr_Capabilities: ndr_push_error(Bad Switch): Bad switch value 2 at librpc/gen_ndr/ndr_netlogon.c:7604

See 'Bad switch value 2' in ndr_netlogon.c.


Update of Samba packages is needed (samba > 4.15.13+git.636.53d93c5b9d6-150400.3.23.1).


The problem here is about the query level in which also uses the numbers 1 and the undocumented 2, which is causing the problems.

One scenario when such issue occurred is when Windows 10 KB5028166 update was applied and the Windows system was authenticating against Samba domain controller.

Additional Information


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  • Document ID:000021140
  • Creation Date: 20-Jul-2023
  • Modified Date:20-Jul-2023
    • SUSE Linux Enterprise Server
    • SUSE Linux Enterprise Server for SAP Applications

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