Ubuntu has issued updates for the kernel. These fixes two vulnerabilities, which can be exploited by malicious, local users to cause a DoS (Denial of Service) or gain escalated privileges.
Apply updated packages. Links to updates 
SUSE has issued updates for multiple packages. These fix various vulnerabilities, which can be exploited by malicious, local users to escalate their privileges and by malicious people to compromise a vulnerable system.
Apply updated packages.
Updated packages are available using YaST Online Update or the SUSE FTP site. Full description .
Noam Rathaus has discovered a vulnerability in KMail, which can be exploited by malicious people to conduct spoofing attacks.
The vulnerability is caused due to an error where HTML code can overlay part of the user interface. This can e.g. be exploited to trick a user into believing a specially crafted mail is signed and coming from a trusted source.
Successful exploitation requires that the option "Prefer HTML to plain text" is enabled (not default setting).
The vulnerability has been confirmed in KMail 1.7.1 on KDE 3.3.1. KDE 3.3.2 is reportedly also affected. Other versions may also be affected.
Disable the "Prefer HTML to plain text" setting. Link .
Red Hat Inc. is warning enterprise Linux users to update their installations of XFree86 to fix a number of serious security bugs, some of which could allow attackers to take over a system. Affected operating systems include Enterprise Linux AS 3, Enterprise Linux ES 3 and Enterprise Linux WS 3, Red Hat said in an advisory. XFree86 is an implementation of the X Window System that provides low-level graphics functionality for graphical user interface systems such as KDE and Gnome. The most serious flaw is an integer overflow in the libXpm library, used by some applications in opening XPixMap images, Red Hat said. An attacker could use a malicious XPixMap file to execute code on a user's system. Source for this one .