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Ubuntu Security Notice USN-3586-2
May 28, 2018

isc-dhcp vulnerabilities
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A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 12.04 ESM

Summary:

Several security issues were fixed in DHCP.

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

Details:

USN-3586-1 fixed a vulnerability in DHCP. This update provides
the corresponding update for Ubuntu 12.04 ESM.

Original advisory details:

 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 12.04 ESM:
  isc-dhcp-client                 4.1.ESV-R4-0ubuntu5.13
  isc-dhcp-relay                  4.1.ESV-R4-0ubuntu5.13
  isc-dhcp-server                 4.1.ESV-R4-0ubuntu5.13
  isc-dhcp-server-ldap            4.1.ESV-R4-0ubuntu5.13

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

References:
  https://usn.ubuntu.com/usn/usn-3586-2
  https://usn.ubuntu.com/usn/usn-3586-1
  CVE-2018-5732, CVE-2018-5733