USN-2950-3: Samba regressions

USN-2950-1 fixed vulnerabilities in Samba. The fixes introduced in Samba
4.3.8 caused certain regressions and interoperability issues.

This update resolves some of these issues by updating to Samba 4.3.9 in
Ubuntu 14.04 LTS, Ubuntu 15.10 and Ubuntu 16.04 LTS. Backported regression
fixes were added to Samba 3.6.25 in Ubuntu 12.04 LTS.

This advisory was inadvertently published as USN-2950-2 originally.

Original advisory details:

Jouni Knuutinen discovered that Samba contained multiple flaws in the
DCE/RPC implementation. A remote attacker could use this issue to perform
a denial of service, downgrade secure connections by performing a
machine-in-the-middle attack, or possibly execute arbitrary code.
(CVE-2015-5370)

Stefan Metzmacher discovered that Samba contained multiple flaws in the
NTLMSSP authentication implementation. A remote attacker could use this
issue to downgrade connections to plain text by performing a
machine-in-the-middle attack. (CVE-2016-2110)

Alberto Solino discovered that a Samba domain controller would establish a
secure connection to a server with a spoofed computer name. A remote
attacker could use this issue to obtain sensitive information.
(CVE-2016-2111)

Stefan Metzmacher discovered that the Samba LDAP implementation did not
enforce integrity protection. A remote attacker could use this issue to
hijack LDAP connections by performing a machine-in-the-middle attack.
(CVE-2016-2112)

Stefan Metzmacher discovered that Samba did not validate TLS certificates.
A remote attacker could use this issue to spoof a Samba server.
(CVE-2016-2113)

Stefan Metzmacher discovered that Samba did not enforce SMB signing even if
configured to. A remote attacker could use this issue to perform a
machine-in-the-middle attack. (CVE-2016-2114)

Stefan Metzmacher discovered that Samba did not enable integrity protection
for IPC traffic. A remote attacker could use this issue to perform a
machine-in-the-middle attack. (CVE-2016-2115)

Stefan Metzmacher discovered that Samba incorrectly handled the MS-SAMR and
MS-LSAD protocols. A remote attacker could use this flaw with a
machine-in-the-middle attack to impersonate users and obtain sensitive
information from the Security Account Manager database. This flaw is
known as Badlock. (CVE-2016-2118)

Samba has been updated to 4.3.8 in Ubuntu 14.04 LTS and Ubuntu 15.10.
Ubuntu 12.04 LTS has been updated to 3.6.25 with backported security fixes.

In addition to security fixes, the updated packages contain bug fixes,
new features, and possibly incompatible changes. Configuration changes may
be required in certain environments.