(RHSA-2016:0010) Moderate: samba4 security update

Samba is an open-source implementation of the Server Message Block (SMB) or
Common Internet File System (CIFS) protocol, which allows PC-compatible
machines to share files, printers, and other information.

A denial of service flaw was found in the LDAP server provided by the AD DC
in the Samba process daemon. A remote attacker could exploit this flaw by
sending a specially crafted packet, which could cause the server to consume
an excessive amount of memory and crash. (CVE-2015-7540)

Multiple buffer over-read flaws were found in the way Samba handled
malformed inputs in certain encodings. An authenticated, remote attacker
could possibly use these flaws to disclose portions of the server memory.
(CVE-2015-5330)

A man-in-the-middle vulnerability was found in the way “connection signing”
was implemented by Samba. A remote attacker could use this flaw to
downgrade an existing Samba client connection and force the use of plain
text. (CVE-2015-5296)

A missing access control flaw was found in Samba. A remote, authenticated
attacker could use this flaw to view the current snapshot on a Samba share,
despite not having DIRECTORY_LIST access rights. (CVE-2015-5299)

An access flaw was found in the way Samba verified symbolic links when
creating new files on a Samba share. A remote attacker could exploit this
flaw to gain access to files outside of Samba’s share path. (CVE-2015-5252)

Red Hat would like to thank the Samba project for reporting these issues.
Upstream acknowledges Stefan Metzmacher of the Samba Team and Sernet.de as
the original reporters of CVE-2015-5296, [email protected] as the original
reporter of CVE-2015-5299, Jan “Yenya” Kasprzak and the Computer Systems
Unit team at Faculty of Informatics, Masaryk University as the original
reporters of CVE-2015-5252 flaws, and Douglas Bagnall as the original
reporter of CVE-2015-5330.

All samba4 users are advised to upgrade to these updated packages, which
contain backported patches to correct these issues. After installing this
update, the smb service will be restarted automatically.