Ubuntu 12.04 LTS USN-1571-1 Moderate: isc-dhcp Denial Of Service

ubuntu

September 18, 2012

DHCP could be made to crash if it received specially crafted network traffic.

Summary

DHCP could be made to crash if it received specially crafted network

traffic.

Software Description:

- isc-dhcp: DHCP server and client

- dhcp3: DHCP server and client

Details:

Glen Eustace discovered that the DHCP server incorrectly handled IPv6

expiration times. A remote attacker could use this issue to cause DHCP to

crash, resulting in a denial of service. This issue only affected Ubuntu

11.04, Ubuntu 11.10 and Ubuntu 12.04 LTS. (CVE-2012-3955)

Dan Rosenberg discovered that the DHCP AppArmor profile could be escaped by

using environment variables. This update mitigates the issue by sanitizing

certain variables in the DHCP shell scripts.

Topics Covered

security advisory denial of service network traffic ubuntu moderate issue dhcp update isc-dhcp

Update Instructions

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

Ubuntu 12.04 LTS:
  isc-dhcp-client                 4.1.ESV-R4-0ubuntu5.5
  isc-dhcp-server                 4.1.ESV-R4-0ubuntu5.5

Ubuntu 11.10:
  isc-dhcp-client                 4.1.1-P1-17ubuntu10.5
  isc-dhcp-server                 4.1.1-P1-17ubuntu10.5

Ubuntu 11.04:
  isc-dhcp-client                 4.1.1-P1-15ubuntu9.6
  isc-dhcp-server                 4.1.1-P1-15ubuntu9.6

Ubuntu 10.04 LTS:
  dhcp3-client                    3.1.3-2ubuntu3.4
  dhcp3-server                    3.1.3-2ubuntu3.4

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