The problem can be corrected by upgrading the affected package to version 2.6.8.1-16.19 (for Ubuntu 4.10), or 2.6.10-34.2 (for Ubuntu 5.04). After doing a standard system upgrade you need to reboot your computer to effect the necessary changes.
Details follow:
Alexander Nyberg discovered that ptrace() insufficiently validated addresses on the amd64 platform so that it was possible to set an invalid segment base. A local attacker could exploit this to crash the kernel. This does not affect the i386 and powerpc platforms in any way. (CAN-2005-0756)
Chris Wright discovered that the mmap() function could create illegal memory maps (using the "mmap" function) with the start address pointing beyond the end address. A local user could exploit this to crash the kernel or possibly even execute arbitrary code with kernel privileges. (CAN-2005-1265)