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Ubuntu Security Notice USN-3586-1
March 01, 2018

isc-dhcp vulnerabilities
==========================================================================

A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 17.10
- Ubuntu 16.04 LTS
- Ubuntu 14.04 LTS

Summary:

Several security issues were fixed in DHCP.

Software Description:
- isc-dhcp: DHCP server and client

Details:

Konstantin Orekhov discovered that the DHCP server incorrectly handled a
large number of concurrent TCP sessions. A remote attacker could possibly
use this issue to cause a denial of service. This issue only affected
Ubuntu 14.04 LTS and Ubuntu 16.04 LTS. (CVE-2016-2774)

It was discovered that the DHCP server incorrectly handled socket
descriptors. A remote attacker could possibly use this issue to cause a
denial of service. (CVE-2017-3144)

Felix Wilhelm discovered that the DHCP client incorrectly handled certain
malformed responses. A remote attacker could use this issue to cause the
DHCP client to crash, resulting in a denial of service, or possibly execute
arbitrary code. In the default installation, attackers would be isolated by
the dhclient AppArmor profile. (CVE-2018-5732)

Felix Wilhelm discovered that the DHCP server incorrectly handled reference
counting. A remote attacker could possibly use this issue to cause the DHCP
server to crash, resulting in a denial of service. (CVE-2018-5733)

Update instructions:

The problem can be corrected by updating your system to the following
package versions:

Ubuntu 17.10:
  isc-dhcp-client                 4.3.5-3ubuntu2.2
  isc-dhcp-relay                  4.3.5-3ubuntu2.2
  isc-dhcp-server                 4.3.5-3ubuntu2.2
  isc-dhcp-server-ldap            4.3.5-3ubuntu2.2

Ubuntu 16.04 LTS:
  isc-dhcp-client                 4.3.3-5ubuntu12.9
  isc-dhcp-relay                  4.3.3-5ubuntu12.9
  isc-dhcp-server                 4.3.3-5ubuntu12.9
  isc-dhcp-server-ldap            4.3.3-5ubuntu12.9

Ubuntu 14.04 LTS:
  isc-dhcp-client                 4.2.4-7ubuntu12.12
  isc-dhcp-relay                  4.2.4-7ubuntu12.12
  isc-dhcp-server                 4.2.4-7ubuntu12.12
  isc-dhcp-server-ldap            4.2.4-7ubuntu12.12

In general, a standard system update will make all the necessary changes.

References:
  https://usn.ubuntu.com/usn/usn-3586-1
  CVE-2016-2774, CVE-2017-3144, CVE-2018-5732, CVE-2018-5733

Package Information:
  https://launchpad.net/ubuntu/+source/isc-dhcp/4.3.5-3ubuntu2.2
  https://launchpad.net/ubuntu/+source/isc-dhcp/4.3.3-5ubuntu12.9
  https://launchpad.net/ubuntu/+source/isc-dhcp/4.2.4-7ubuntu12.12