USN-1571-1: DHCP vulnerability

Releases

• Ubuntu 12.04
• Ubuntu 11.10
• Ubuntu 11.04
• Ubuntu 10.04

Packages

• dhcp3 - DHCP server and client
• isc-dhcp - 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.

Update instructions

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

Ubuntu 12.04

• isc-dhcp-server - 4.1.ESV-R4-0ubuntu5.5
• isc-dhcp-client - 4.1.ESV-R4-0ubuntu5.5

Ubuntu 11.10

• isc-dhcp-server - 4.1.1-P1-17ubuntu10.5
• isc-dhcp-client - 4.1.1-P1-17ubuntu10.5

Ubuntu 11.04

• isc-dhcp-server - 4.1.1-P1-15ubuntu9.6
• isc-dhcp-client - 4.1.1-P1-15ubuntu9.6

Ubuntu 10.04

• 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.

References

• CVE-2012-3955
• https://launchpad.net/bugs/1016643