[USN-803-2] Dhcp vulnerability

By | 2010/01/27

The following security announcement applies to dhcp-client. If you have dhcp-client installed, please see below for details on the vulnerability and instructions on patching your system:

USN-803-1 fixed a vulnerability in Dhcp. Due to an error, the patch to
fix the vulnerability was not properly applied on Ubuntu 8.10 and higher.
Even with the patch improperly applied, the default compiler options
reduced the vulnerability to a denial of service. Additionally, in Ubuntu
9.04 and higher, users were also protected by the AppArmor dhclient3
profile. This update fixes the problem.

Original advisory details:

It was discovered that the DHCP client as included in dhcp3 did not verify
the length of certain option fields when processing a response from an IPv4
dhcp server. If a user running Ubuntu 6.06 LTS or 8.04 LTS connected to a
malicious dhcp server, a remote attacker could cause a denial of service or
execute arbitrary code as the user invoking the program, typically the
‘dhcp’ user. For users running Ubuntu 8.10 or 9.04, a remote attacker
should only be able to cause a denial of service in the DHCP client. In
Ubuntu 9.04, attackers would also be isolated by the AppArmor dhclient3

The above security vulnerabilities apply to the following Ubuntu releases:

  • Ubuntu 8.10
  • Ubuntu 9.04
  • Ubuntu 9.10

If you are have this utility installed on your Ubuntu system you’ll need to apply the security update to be protected. Please follow the steps below to ensure your system is properly patched:

Apply Updates

To apply the updates run the following command(s) within your Terminal:

sudo aptitude update
sudo aptitude safe-upgrade

After a standard system upgrade you need to restart any DHCP network connections utilizing dhclient3 to effect the necessary changes.