Attachment 18119 Details for Bug 15473 – Advisory v2

Advisory v2

CVE-2023-42670-busy-rpc-DoS-master-v2.txt (text/plain), 2.47 KB, created by Andrew Bartlett on 2023-09-25 04:10:57 UTC

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Creator: Andrew Bartlett

Created: 2023-09-25 04:10:57 UTC

Size: 2.47 KB

patch

obsolete

>===========================================================
>== Subject:     Samba AD DC Busy RPC multiple listener DoS
>==
>== CVE ID#:     CVE-2023-42670
>==
>== Versions:    All versions of Samba since Samba 4.16
>==
>== Summary:     Samba can be made to start multiple incompatible RPC
>                listeners, disrupting service on the AD DC.
>===========================================================
>
>===========
>Description
>===========
>
>Samba as an Active Directory DC operates RPC services from two
>distinct parts of the codebase.  Those services focused on the AD DC
>are started in the main "samba" process, while services focused on the
>fileserver and NT4-like DC are started from the new samba-dcerpcd,
>which is launched on-demand from the fileserver (smbd) tasks.
>
>When starting, samba-dcerpcd must first confirm which services not to
>provide, so as to avoid duplicate listeners.
>
>The issue in this advisory is that, when Samba's RPC server is under
>load, or otherwise not responding, the the servers NOT built for the
>AD DC (eg build instead for the NT4-emulation "classic DCs") can be
>incorrectly started, and compete to listen on the same unix domain
>sockets.
>
>This then results in some queries being answered by the AD DC, and
>some not.  This has been seen in production at multiple sites, as "The
>procedure number is out of range" when starting Active Directory Users
>and Computers tool, however it can also be triggered maliciously, to
>prevent service on the AD DC.
>
>==================
>Patch Availability
>==================
>
>Patches addressing both these issues have been posted to:
>
>    https://www.samba.org/samba/security/
>
>Additionally, Samba $VERSIONS have been issued
>as security releases to correct the defect.  Samba administrators are
>advised to upgrade to these releases or apply the patch as soon
>as possible.
>
>==================
>CVSSv3 calculation
>==================
>
>CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H (6.5)
>
>==========
>Workaround
>==========
>
>Setting "rpc start on demand helpers = no" in the smb.conf will
>disable the file-server based RPC servers entirely.  While used less
>often, these services are required so this is not a long-term solution.
>
>=======
>Credits
>=======
>
>Originally reported by Andrew Bartlett of Catalyst and the Samba Team.
>
>Patches provided by Andrew Bartlett of Catalyst and the Samba Team.
>
>==========================================================
>== Our Code, Our Bugs, Our Responsibility.
>== The Samba Team
>==========================================================
>

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