Thomas Biege discovered a flaw in the privilege dropping of the NTP server. When ntpd was configured to drop root privileges, and the group to run under was specified as a name (as opposed to a numeric group ID), ntpd changed to the wrong group. Depending on the actual group it changed to, this could either cause non-minimal privileges, or a malfunctioning ntp server if the group does not have the privileges that ntpd actually needs.
On Ubuntu 4.10, ntpd does not use privilege dropping by default, so you are only affected if you manually activated it. In Ubuntu 5.04, privilege dropping is used by default, but this bug is already fixed.
2 September 2005
A security issue affects these releases of Ubuntu and its derivatives:
Thomas Biege discovered a flaw in the privilege dropping of the NTP server. When ntpd was configured to drop root privileges, and the group to run under was specified as a name (as opposed to a numeric group ID), ntpd changed to the wrong group. Depending on the actual group it changed to, this could either cause non-minimal privileges, or a malfunctioning ntp server if the group does not have the privileges that ntpd actually needs.
On Ubuntu 4.10, ntpd does not use privilege dropping by default, so you are only affected if you manually activated it. In Ubuntu 5.04, privilege dropping is used by default, but this bug is already fixed.
The problem can be corrected by updating your system to the following package versions:
To update your system, please follow these instructions: https://wiki.ubuntu.com/Security/Upgrades.
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