How to find Samba v4 instances

How to find Samba v4 instances #

On October 10th, the Samba team announced an interesting vulnerability that could allow a remote attacker to connect to unix stream sockets on the Samba server. The issue occurs when a RPC service name is requested that contains a unix directory traversal sequence (../). The vulnerability is being tracked as CVE-2023-3961 and may enable remote code execution and esclation of privilege attacks using system-specific unix stream sockets. These sockets are typically used for interprocess communication and commercial NAS vendors may be more exposed than a standard systemd-based Linux installations. The Samba project scored this as CVSS 3.1: AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:H/A:N (6.8), but the actual risk may vary drastically by implementation.

What is the risk? #

The actual risk may vary wildly given the different implementations of Samba across open source and commercial systems. On a typical Ubuntu Linux (22.04) system, unix stream sockets associated with the core systemd service (system_bus_socket) may enable denial of service at the least. In commercial implementations, such as Synology NAS devices, the exposed unix stream sockets may expose much more:

/run/filestation/thumbd.sock
/run/postgresql/.s.PGSQL.5432
/run/recycle_bin/daemon.sock
/run/samba/nmbd/unexpected
/run/syno_background_task.sock
/run/synocached.sock
/run/synologan.sock
/run/synoscgi_domain_socket.sock
/run/synoscgi-fastapi.sock
/run/synoscgi.sock
/run/synoscgi_socket.sock
/run/syslog-ng/syslog-ng.ctl
/run/systemd/journal/stdout
/run/systemd/private
/run/udev/control
/tmp/iscsi/plugin_server.sock
/tmp/rtsp_socket_server
/tmp/S2S/daemon.sock
/tmp/ssmessaged.sock
/tmp/ssmobiled.sock
/tmp/ssrtpdataprovider.sock
/tmp/sswebstreamd.sock
/tmp/synosnmpcd.sock
/tmp/synotaskmgr.sock
/tmp/synotokenmgr.sock
/tmp/synowstransfer.sock
/var/run/dbus/system_bus_socket
/var/run/synobackupd.socket
/var/run/synocgid/synocgid.apikey.get.socket
/var/run/synocgid/synocgid.checkreplayattack.socket
/var/run/synocgid/synocgid.htua.socket
/var/run/synocgid/synocgid.remove.by.attr.socket
/var/run/synocgid/synocgid.remove.user.socket
/var/run/synocgid/synocgid.session.add.socket
/var/run/synocgid/synocgid.session.check.socket
/var/run/synocgid/synocgid.session.crypto.box.socket
/var/run/synocgid/synocgid.session.exist.socket
/var/run/synocgid/synocgid.session.getbyid.socket
/var/run/synocgid/synocgid.session.getid.socket
/var/run/synocgid/synocgid.session.get.socket
/var/run/synocgid/synocgid.session.resume.socket
/var/run/synocgid/synocgid.session.update.socket
/var/run/synocgid/synocgid.session.write.to.file.socket
/var/run/synocgid/synocgid.ssldecrypt.socket
/var/run/synoelasticd.sock

What is Samba? #

Samba is an incredibly popular open source software project that describes itself as “the standard Windows interoperability suite of programs for Linux and Unix”. Samba is used in most implementations of SMB/CIFS outside of Microsoft Windows, Apple macOS, and a few commercial network storage vendors. In short, Samba is used to enable SMB file transfers, and to power Active Directory implementations without Microsoft Windows servers.

Are updates available? #

The Samba team has issued updates in versions 4.19.1, 4.18.8 and 4.17.12 to address this issue. Samba is widely used across many devices and virtual appliances, including common network attached storage (NAS) and file server functionality on Linux-based routers. Updates to all distributions, packaging formats, and commercial variants may take considerable time to become available.

How do I find potentially vulnerable versions of Samba with runZero? #

Samba v4 services can be found by navigating to the Service Inventory and using the following pre-built query:

_asset.protocol:smb protocol:smb product:samba _service.product:"Samba:Samba:4"

Results from the above query should be triaged to determine if they require patching or vendor intervention.

As always, any prebuilt queries are available from your runZero console. Check out the documentation for other useful inventory queries.

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