RHSA-2016:0621 - Security Advisory

Topic

An update for samba is now available for Red Hat Enterprise Linux 5.

Red Hat Product Security has rated this update as having a security impact of
Important. A Common Vulnerability Scoring System (CVSS) base score, which gives
a detailed severity rating, is available for each vulnerability from the CVE
link(s) in the References section.

[Updated 14 April 2016]
This advisory previously incorrectly listed the CVE-2016-2112 issue as addressed
by this update. However, this issue did not affect the samba packages on Red Hat
Enterprise Linux 5. The CVE-2016-2115 was also incorrectly listed as addressed
by this update. This issue does affect the samba packages on Red Hat Enterprise
Linux 5. Customers are advised to use the "client signing = required"
configuration option in the smb.conf file to mitigate CVE-2016-2115. No changes
have been made to the packages.

Description

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

Security Fix(es):

• A protocol flaw, publicly referred to as Badlock, was found in the Security

Account Manager Remote Protocol (MS-SAMR) and the Local Security Authority
(Domain Policy) Remote Protocol (MS-LSAD). Any authenticated DCE/RPC connection
that a client initiates against a server could be used by a man-in-the-middle
attacker to impersonate the authenticated user against the SAMR or LSA service
on the server. As a result, the attacker would be able to get read/write access
to the Security Account Manager database, and use this to reveal all passwords
or any other potentially sensitive information in that database. (CVE-2016-2118)

• Several flaws were found in Samba's implementation of NTLMSSP authentication.

An unauthenticated, man-in-the-middle attacker could use this flaw to clear the
encryption and integrity flags of a connection, causing data to be transmitted
in plain text. The attacker could also force the client or server into sending
data in plain text even if encryption was explicitly requested for that
connection. (CVE-2016-2110)

• It was discovered that Samba configured as a Domain Controller would establish

a secure communication channel with a machine using a spoofed computer name. A
remote attacker able to observe network traffic could use this flaw to obtain
session-related information about the spoofed machine. (CVE-2016-2111)

Red Hat would like to thank the Samba project for reporting these issues.
Upstream acknowledges Stefan Metzmacher (SerNet) as the original reporter of
CVE-2016-2118 and CVE-2016-2110.

Solution

For details on how to apply this update, which includes the changes described in
this advisory, refer to:

https://access.redhat.com/articles/11258

After installing this update, the smb service will be restarted automatically.

Affected Products

• Red Hat Enterprise Linux Server 5 x86_64
• Red Hat Enterprise Linux Server 5 ia64
• Red Hat Enterprise Linux Server 5 i386
• Red Hat Enterprise Linux Workstation 5 x86_64
• Red Hat Enterprise Linux Workstation 5 i386
• Red Hat Enterprise Linux Desktop 5 x86_64
• Red Hat Enterprise Linux Desktop 5 i386
• Red Hat Enterprise Linux for IBM z Systems 5 s390x
• Red Hat Enterprise Linux for Power, big endian 5 ppc
• Red Hat Enterprise Linux Server from RHUI 5 x86_64
• Red Hat Enterprise Linux Server from RHUI 5 i386

Fixes

• BZ - 1311893 - CVE-2016-2110 samba: Man-in-the-middle attacks possible with NTLMSSP authentication
• BZ - 1311902 - CVE-2016-2111 samba: Spoofing vulnerability when domain controller is configured
• BZ - 1317990 - CVE-2016-2118 samba: SAMR and LSA man in the middle attacks

CVEs

• CVE-2016-2118
• CVE-2016-2111
• CVE-2016-2110

References

• https://access.redhat.com/security/updates/classification/#important
• https://access.redhat.com/security/vulnerabilities/badlock
• https://access.redhat.com/articles/2253041
• http://badlock.org/
• https://access.redhat.com/articles/2243351