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Yesterday, November 27th, the Ubuntu developers discovered yet another security issue (actually, more than one) in the Linux kernel packages. These vulnerabilities affect the following Ubuntu distributions: 6.06 LTS, 7.10, 8.04 LTS and 8.10 (also applies to Kubuntu, Edubuntu and Xubuntu). The truth is that there are exactly nine (yes, 9) security issues (see below for details), therefore, it is strongly recommended to update your system as soon as possible!

The Ubuntu developers discovered that:

1. The Xen hypervisor block driver couldn't accurately validate incoming requests. Therefore, a user with root privileges could crash a system and cause a DoS (Denial of Service) attack by executing malicious I/O requests. This issue affects only Ubuntu 7.10.

2. The i915 video driver couldn't accurately validate memory addresses. Therefore, an attacker could remap memory and cause a system crash, leading to a DoS (Denial of Service) attack. Ubuntu 6.06 LTS, 7.10 and 8.04 LTS users are not affected by this issue. Ubuntu 8.10 users should update their systems to correct this vulnerability!

3. When files were created in the setgid directories, the Linux kernel package couldn't accurately strip permissions. Because of this, a local user could gain extra group privileges. This issue was discovered by David Watson and it affects only Ubuntu 6.06 LTS users!

4. When file splice requests were handled, the Linux kernel package couldn't accurately reject the "append" flag. Therefore, a local attacker could create changes to random locations in a file by bypassing the append mode. This issue was discovered by Olaf Kirch and Miklos Szeredi, and affects only Ubuntu 7.10 and 8.04 LTS users!

5. The SCTP stack couldn't accurately handle INIT-ACK. Because of this, a remote user could send specially crafted SCTP traffic and crash the system, leading to a DoS (Denial of Service) attack. This issue affects only Ubuntu 8.10 users!

ATTENTION Ubuntu 6.06 LTS, 7.10 and 8.04 users: Due to an unavoidable ABI change, the kernel packages have a new version number, which will force you to reinstall or recompile all third-party kernel modules you might have installed. For example, after the upgrade to the above version of your kernel package, a software such as VirtualBox will NOT work anymore, therefore you must recompile its kernel module by issuing a specific command in the terminal. Moreover, if you use the linux-restricted-modules package, you have to update it as well to get modules that work with the new Linux kernel version. This does not apply to Ubuntu 8.10 users because of DKMS (Dynamic Kernel Module Support). 

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