CVE-2017-7494: samba: authenticated remote code execution from a writable share

This document (7019508) is provided subject to the disclaimer at the end of this document.

Environment

SUSE Linux Enterprise Server 12 Service Pack 2 (SLES 12 SP2)
SUSE Linux Enterprise Server 12 Service Pack 1 (SLES 12 SP1)
SUSE Linux Enterprise Server 12 LTSS

SUSE Linux Enterprise Server 11 Service Pack 4 (SLES 11 SP4)
SUSE Linux Enterprise Server 11 Service Pack 3 (SLES 11 SP3) LTSS
SUSE Linux Enterprise Server 11 Service Pack 2 (SLES 11 SP2) LTSS

Situation

On May 24th 2017 the Samba team published a fix for a remote root code execution in Samba.

All versions of Samba from 3.5.0 on-wards are vulnerable to a remote code execution vulnerability, allowing a malicious client to upload a shared library to a writable share, and then cause the server to load and execute it.

Resolution

SUSE is aware of this issues and has already released patches via the respective product updates channels.

The following products are affected:

SLES 12 SP2

SUSE released samba-4.4.2-38.6.1 on the 24th of May 2017

SLES 12 SP1

SUSE released samba-4.2.4-28.14.1 on the 24th of May 2017

SLES 12 GA (LTSS)

SUSE released samba-4.2.4-18.41.1 on the 24th of May 2017

SLES 11 SP4

SUSE released samba-3.6.3-93.1 on the 24th of May 2017

SLES 11 SP3 (LTSS)

SUSE released samba-3.6.3-93.1 on the 24th of May 2017

Workarounds:

Having the Samba shares mounted 'noexec' on the server would block the loading of malicious code from these shares directly.
By adding the following parameter to the [global] section in the smb.conf you can prevent clients from accessing any names pipe entpoints:
- nt pipe support = no
Please note that this can disable some expected functionality for Windows clients.

Cause

For details on this samba vulnerability please visit:
https://www.samba.org/samba/security/CVE-2017-7494.html

Additional Information

Patches and further information can be found in the CVE:

https://www.suse.com/security/cve/CVE-2017-7494/

AppArmor

If AppArmor is active, /usr/share/samba/update-apparmor-samba-profile is used to dynamically generate profiles with rwlk preventing a possible exploit.

Not Affected:
SUSE Linux Enterprise Server 11 Service Pack 1 (SLES 11 SP1)

Disclaimer

This Support Knowledgebase provides a valuable tool for SUSE customers and parties interested in our products and solutions to acquire information, ideas and learn from one another. Materials are provided for informational, personal or non-commercial use within your organization and are presented "AS IS" WITHOUT WARRANTY OF ANY KIND.